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Relations And Functions

Question
CBSEENMA12036142

integral subscript 0 superscript straight pi[cot x]dx, where [.] denotes the greatest integer function, is equal to
  • π/2

  • 1

  • -1

  • – π/2 

Solution

D.

– π/2 

Let space straight I space space equals space integral subscript 0 superscript straight pi space left square bracket space cot space straight x right square bracket space dx space space... space left parenthesis 1 right parenthesis
space equals space integral subscript 0 superscript straight pi space left square bracket space cot space left parenthesis straight pi minus straight x right parenthesis right square bracket space dx space equals space integral subscript 0 superscript straight x left square bracket negative cot space straight x right square bracket space dx space space... space left parenthesis 2 right parenthesis
adding space left parenthesis 1 right parenthesis space and space left parenthesis 2 right parenthesis
2 straight I space equals space integral subscript 0 superscript straight pi space left square bracket space cot space straight x right square bracket space dx space space plus space integral subscript 0 superscript straight pi left square bracket negative cot space straight x right square bracket space dx space space equals integral subscript 0 superscript straight pi space left parenthesis negative 1 right parenthesis dx
equals space left square bracket negative straight x right square bracket subscript 0 superscript straight pi space equals space minus space straight pi
therefore comma space straight I space equals space straight pi over 2

Some More Questions From Relations and Functions Chapter

lf a matrix has 18 elements, what are the possible orders it can have ? What, if it has 5 elements?

If a matrix A has 12 elements, what arc the possible orders it can have 7 What if it has 7 elements ?

Let A be the set of all students of a boys school. Show that the relation R in A given by R = {(a, b) : a is sister of b} is the empty relation and R’ = {(a, b) : the difference between heights of a and b is less than 3 meters} is the universal relation.

Show that the relation R in the set {1, 2, 3} given by R = {(1, 1), (2, 2), (3, 3), (1, 2), (2, 3)} is reflexive but neither symmetric nor transitive.

Show that the relation R in the set {1, 2, 3} given by R = {(1, 2), (2, 1)} is symmetric but neither reflexive nor transitive.

Give an example of a relation which is

(i) Symmetric but neither reflexive nor transitive.
(ii) Transitive but neither reflexive nor symmetric.
(iii) Reflexive and symmetric but not transitive.
(iv) Reflexive and transitive but not symmetric.
(v) Symmetric and transitive but not reflexive.

Let L be the set of all lines in a plane and R be the relation in L defined as R = {(L1, L2) : L1 is perpendicular to L2}. Show that R is symmetric but neither reflexive nor transitive.

 Determine whether each of the following relations are reflexive, symmetric and transitive :

(i) Relation R in the set A = {1, 2, 3,....., 13, 14} defined as

R = {(x, y) : 3 x – y = 0}

(ii) Relation R in the set N of natural numbers defined as R = {(x, y) : y = x + 5 and x < 4} (iii) Relation R in the set A = {1, 2, 3, 4, 5, 6} as R = {(x,y) : y is divisible by x} (iv) Relation R in the set Z of all integers defined as R = {(x,y) : x – y is an integer}

(v) Relation R in the set A of human beings in a town at a particular time given by
(a)    R = {(x, y) : x and y work at the same place}
(b)    R = {(x,y) : x and y live in the same locality}
(c)    R = {(x, y) : x is exactly 7 cm taller than y}
(d)    R = {(x, y) : x is wife of y}
(e)    R = {(x,y) : x is father of y}

Check whether the relation R defined in the set {1, 2, 3, 4, 5, 6} as R = {(a, b) : b = a + 1} is reflexive, symmetric or transitive.