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Explain solution rd sharma class 12 chapter 16 Increasing and decreasing function exercise multiple choice question, question 35

Answers (1)

Always increases (Option a)

Hints: Find the derivative of functions

Given: f(x)=\tan x-x

Solution:

We have,              \begin{aligned} &f(x)=\tan x-x \\ &f^{\prime}(x)=\sec ^{2} x-1>0 \end{aligned}

                              Or

                   \begin{aligned} &\sec ^{2} x>1 \end{aligned}

Now

               \begin{aligned} &\cos x \in[-1,1] \\ &\sec x \in(-\infty,-1] \cup[1, \infty) \end{aligned}

Thus,

               \sec ^{2} x \in[1, \infty)

Hence,

               f^{\prime}(x)>0 \forall x

Function f(x)=\tan x-x is always increasing.

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