Limit Continuity And Differentiability Ques 38

  1. Match the conditions/expressions in Column I with statement in Column II
Column I Column II
A. $\sin (\pi[x])$ p. differentiable everywhere
B. $\sin \{\pi(x-[x])\}$ q. no where differentiable
r. not differentiable at 1 and -1

(1992, 2M)

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Answer:

Correct Answer: 38.$(A) \rightarrow \mathrm{p}$ ; $ (B) $ $\rightarrow \mathrm{r}$

Solution: We know, $[x] \in I, \forall x \in R$.

Therefore, $\sin (\pi[x])=0, \forall x \in R$.

By theory, we know that $\sin (\pi[x])$ is differentiable everywhere, therefore (A) $\leftrightarrow$ (p).

Again, $f(x)=\sin \{\pi(x-[x])\}$

Now, $ x-[x]=\{x\}$

then $\pi(x-[x])=\pi\{x\}$

which is not differentiable at $x \in I$.

Therefore, $(B) \leftrightarrow(r)$ is the answer.



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