Application of Derivatives — Maths STD 12 Science — Question
Gujarat BoardEnglish MediumSTD 12 ScienceMathsApplication of Derivatives1 Mark
MCQ
The function $(x-\sin x)$ decreases for
A
all $x$
B
$x<\frac{\pi}{2}$
C
0 < X < $\frac{\pi}{4}$
D
no value of $x$
✓
Answer
Let $f(x)=x-\sin x$ Differentiating w.r.t. $x$, we get $f^{\prime}(x)=1-\cos x$ For function to be decreasing, $f^{\prime}(x)<0$ $\Rightarrow 1-\cos x<0 \Rightarrow \cos x>1$, which is not possible, because maximum value of $\cos x$ is 1 . $\therefore \quad f(x)=(x-\sin x)$ doesn't decrease at any value of $x$.
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