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Relations And Functions

Question
CBSEENMA12036163

Let f(x) = open curly brackets table attributes columnalign left end attributes row cell left parenthesis straight x minus 1 right parenthesis space sin space open parentheses fraction numerator 1 over denominator straight x minus 1 end fraction close parentheses end cell row cell 0 comma space space space space space space space space space space space space space space space space space space space space space space space space space space space if space straight x space equals 1 space space space space space space space space space space end cell end table close comma space if space straight x space not equal to space 1Then which one of the following is true?

  • f is neither differentiable at x = 0 nor at x = 1

  • f is differentiable at x = 0 and at x = 1

  • f is differentiable at x = 0 but not at x = 1 

  • f is differentiable at x = 1 but not at x = 0

Solution

A.

f is neither differentiable at x = 0 nor at x = 1

straight f apostrophe left parenthesis 1 right parenthesis space equals space limit as straight h rightwards arrow 0 of space fraction numerator straight f left parenthesis 1 plus straight h right parenthesis space minus space straight f left parenthesis 1 right parenthesis over denominator straight h end fraction
rightwards double arrow space straight f apostrophe left parenthesis 1 right parenthesis space equals space limit as straight h rightwards arrow 0 of space fraction numerator left parenthesis 1 plus straight h minus 1 right parenthesis space sin space open parentheses begin display style fraction numerator 1 over denominator 1 plus straight h minus 1 end fraction end style close parentheses minus 0 over denominator straight h end fraction
space equals space limit as straight h rightwards arrow 0 of straight h over straight h space sin space open parentheses 1 over straight h close parentheses
rightwards double arrow space straight f apostrophe space left parenthesis 1 right parenthesis space space equals space limit as straight h rightwards arrow 0 of space sin space open parentheses 1 over straight h close parentheses
therefore space straight f space is space not space differentiable space at space straight x space equals 1
similarly space straight f apostrophe left parenthesis 0 right parenthesis space equals space limit as straight h rightwards arrow 0 of space fraction numerator left parenthesis straight h minus 1 right parenthesis space sin space open parentheses begin display style fraction numerator 1 over denominator straight h minus 1 end fraction end style close parentheses minus space sin space left parenthesis 1 right parenthesis over denominator straight h end fraction
⇒ f is also not differentiable at x = 0

Some More Questions From Relations and Functions Chapter

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.

Show that the relation R in R defined as R = {(a, b) : a ≤ b}, is reflexive and transitive but not symmetric.