Limit Continuity and Differentiability 7 Question 18

18. Which of the following functions is differentiable at x=0 ?

(2001, 2M)

(a) cos(|x|)+|x|

(b) cos(|x|)|x|

(c) sin(|x|)+|x|

(d) sin(|x|)|x|

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Answer:

Correct Answer: 18. (b)

Solution:

  1. Given, x2+y2=1

On differentiating w.r.t. x, we get

2x+2yy=0x+yy=0.

Again, differentiating w.r.t. x, we get

1+yy+yy=01+(y)2+yy=0



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