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hi all of you welcome back to ramadin
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maths academy
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okay sorry for all uh because uh
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e4 friday's new videos posted
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because of the wi-fi and uh some another
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problems
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okay and don't need to worry about
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madame videos a proposed just arrow
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exams
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okay don't worry i'm here to help you
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but
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logic and proofs means discrete
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mathematics
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first chapter logical equivalence truth
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tables
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five videos chess you know this is the
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sixth lecture
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in our discrete mathematics logic and
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proofs
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today's topic is predicates first of all
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what is the predicate
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actually in logical groups we have two
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types of logics is there one
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is the logically a propositional logic
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and another one is the
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predicate logic okay here today we are
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going to discuss the predicate it's very
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simple no need to worry
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you probably couldn't find videos of a
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question
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and predicates too and uh remaining
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videos
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but be careful this is a very most
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important topic
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in your first chapter in discrete
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mathematics okay now
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uh you put a predicate i said what is
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the predicate predicate and then we
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suppose i'll consider one statement
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listen carefully it's very important
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suppose x
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is greater than 3 beta x is greater than
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3 then what is the predicate and how
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we are defined this suppose in terms of
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how we can
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write x greater than 3 x is
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greater than
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3 x is a
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variable
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one is the variable another one is the
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logic that is see this x is the
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variable now that is called the subject
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that is called the subject of the
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statement
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and greater than three e greater than
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three
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months that is the predicate of the
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statement the nuance
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logic is it clear x is greater than
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three
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here x is the subject and three is
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greater than
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three this is our predicate
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okay statement even right
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now p of x
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is nothing but the predicate p is what
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better
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predicate okay x is what
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that is a variable okay
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x is what the variable we can define the
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statement
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like this also now i'll give uh some
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examples of
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predicates
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[Music]
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sometimes either it may be true or it
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may be
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false depends upon the statement okay
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let p of x denotes the statement x is
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greater than three
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and a germany gamma naturally x is
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greater than three
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okay what are the truth values of
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p r four and p of two and to narrow
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actually first of all what is the
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predicate of the statement we already
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discussed what is the predicate here
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then predicate any more to the beta x
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greater than three k
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p of x is the predicate here p is the
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predicate and x is a
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variable okay our predicate is greater
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than three
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if you consider in the place of p and
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event nano this is what this is what is
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a given statement
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here how we can write the predicate
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is what x greater than three the
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predicate
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is what the predicate
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is x greater than three and they can
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even each have to
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find out p half 4 we can write
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x greater than 3 in terms of the
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predicate we can write p
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of x okay if you consider p
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of 4 means in the place of x what we
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have to do
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substitute 4 then it will become 2 if
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you consider
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p of 4 if p of 4
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and 20 then x is equal to
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4 x is equal to 4 this
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4 is greater than 3 means what
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p of 4 is a true this this is having
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truth value okay or else you can write
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it is
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false therefore therefore
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p of 4 is
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true what is the truth value of this p
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of 4 is true then check it p of 2
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okay we have 2 we have to ante
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explicitly in this call new to this
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quality what is our statement x is
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greater than three
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if you consider two is greater than
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three
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a one two nano x is e or else you can
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write x is equal to 2
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in the predicate logic then 2 is greater
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than
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3 this is what which is wrong statement
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2 is greater than 3 no therefore when we
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even write
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minimum therefore p of 2
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is false is not
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false like that you can verify whether
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the statement is true
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or false by using predicate logic and
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one more example an important one is
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qr fix denotes the statement x is equal
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to y
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plus 3 this is x is equal to y plus 3
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listen carefully what are the truth
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values of
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proposition q of 1 comma two q
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of three comma zero first of all the
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given
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logic you can write in terms of
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predicate
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eighth german key x is equal to y plus
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three we need
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to predict
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what is the given statement here ah
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they already defined in terms of q along
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the x and y log the and then the
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the function the predicate logic it
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defines in terms
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of it could be of x law denote this
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requirement
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narrow q of x comma y here x and y
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are the variables what is the condition
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the condition is x is equal to y plus 3
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that is the predicate
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in that case what we have to do now i
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will going to consider this
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here my logic intended what is the given
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one here
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x is equal to y plus 3 here
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what is our x value x is equal to 1
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and y is equal to 2 put here what will
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happen
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this is 2 plus 3 this is what 1
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is equal to 5 no it is a false
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then you can write it as it is a false
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therefore
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therefore q of 1 comma
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2 the predicate is false like that
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you can write the truth values of the
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predicates now consider
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this here x is equal to what 3 y is
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equal to what
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0 then how we are going to write what is
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the statement y is equal to x is equal
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to y plus 3
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3 is equal to what beta here y is 0 3
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both are same and the empty the
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statement predicate logic sometimes
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either it may be true
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or it may be false okay
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therefore in dq
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zero is true in the
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predicate logic is it clear just note
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okay it
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statement in predicate logic in that
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compound statement means
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we have two or more statements or
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minimum two statements is there
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by using our connectives what is our
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connectives
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conjunction disjunction and
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implication by implication by using
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these four you have to write the
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combination of those
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statements that is the compound
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statement of the
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predicates statements
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a teacher her teaching is good this is
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one statement and this is another
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statement here what we have to do
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in ehm understand the first statement
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rama is a teacher
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and her teaching is good
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i'm contented antibodies over
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here what is our connective conjunction
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what is that anthony indicate then
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condom on the first of all you have to
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identify
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which is the subject and which is the
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predicate in the given statement
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[Music]
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that is what our subject rama is a
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subject then what is ramay's
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teacher teacher means it indicates the
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logic that is what it it is what
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predicate predicate
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and in even write you or we can
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write it as predicate logic
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and then the predicate teacher predicate
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me teacher
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okay and
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her teaching is good and here
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teaching is the subject
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teaching is the subject good
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is the predicate okay then how we are
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going to write predicate logic is what
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it stands
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good then what is the variable here
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teaching means you can write t
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like this
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okay this is what the
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compound statement how we are going to
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write the compound statement by using
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the connective also
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kind or then or
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if and only
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we already know that how we are going to
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write the predicate rama is a teacher
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rama is the variable subject and t is
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the
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teacher predicate or r means
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like this her teaching is good means or
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teaching
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is the subject good is the predicate
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means what
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g of t then even i cho t of
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r then then and entry
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like this implies
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g of t okay like that we can write the
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compound statements of the predicates
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next we will discuss the
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quantifiers okay
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see all of you next and most important
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one is the quantifier quantifier
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statement quantifier and the intent
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suppose just just observe these four
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statements
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okay or prepositions
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anything all students have books
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okay all students having books that is
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one statement
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and some moments are tall or short
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now whatever it may be but here hall and
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some it could have
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no one sit in the class no one
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for every integer x x square
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is non-negative integer in these
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four statements in this four statement
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all some know one for every each and
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every
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statement indicates by using these four
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values
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these four terms those terms are called
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it as
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quantifiers you know in this statement
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all sum no one there exist or for every
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like that that is associated with some
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quantity or with some statement those
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statements are called it as what
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quantifiers in the quantifiers we have
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two types one is the universal
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quantifier
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then another one is the existential
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quantifier now we will discuss what is
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universal quantifier
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and what is the existential quantifier
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law
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see all of you here universal quantifier
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universal quantifier
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but for all all values and this
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kundalini call it that is universal
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i want to know the universal quantifier
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of p of x is the statement what is the
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statement here
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p of x for all values of x
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and the universal law for all values and
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you mentioned just arrow
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in the domain d for example
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[Music]
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is the universal quantifier of the
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predicate
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p of x and here for all
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is called what universal quantifier
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this is the universal quantifier
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here we read it as for all p x
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or else for every x p x and j
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for example i'll consider one small
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statement p of x this
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statement x plus 1 greater than x
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what is the truth values of the
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quantifier
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for all x p of x where the domain
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consists
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for all the real numbers and into the
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the given statement of the predicator p
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of x
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is what x plus 1 is greater than
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x okay that is the given statement
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then how we are going to write the
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quantifier
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p of x is true why because for all
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values of the real numbers
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you know the statement which
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when it is true uh of the quantifier
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all the real values and payment render
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this is the statement
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if you consider the quantifier of the
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statement in terms of
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pr x it is true
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for all true for all
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the real numbers x is for all
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real numbers the quantifier
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for all x p x is true okay
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like that you can write the universal
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quantifiers now
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next we'll discuss the existential
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quantifiers okay now down
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see existential quantifier and indent
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then there exist at least one element in
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the
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given statement for example i will
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consider qr fix
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denotes the statement what is our
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statement x is equal to
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x plus 3 and here what
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is the truth values of the
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quantification
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of there exist x belongs to q of x
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where the domain consists for all real
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numbers
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what is our given statement first you
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have to write the
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given statement consider it as p q of x
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for your wish p of x
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okay that is one statement x is equal to
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x plus 3 then q of x is true
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when it is for all real numbers
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okay if you take for all real numbers
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the statement is true if you take one
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then it will what will happen one is
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equal to what
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one is equal to had one plus three and
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demo
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one is equal to four both are equal no
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for all real numbers it is not
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true and the rexist x
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q of x is false means this is not
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existence okay this is the existential
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quantifier
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[Music]
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thanks for watching