Question

The subtangent at $x = \pi /2$ on the curve $y = x \sin x$ is

• A. $0$
• B. $1$
• C. $\pi /2$
• D. $none\, of\, these$

Answer 1

Answer: (A)

$0$

Answer 2

We have, $y = x \sin x$
Length of subtangent = $\frac{y}{\frac{dy}{dx}}$
$\Rightarrow \frac{dy}{dx} =x\left(\cos x\right)+\sin x$
Length of subtangent at $x=\frac{\pi}{2}$
$= \frac{0}{\frac{\pi}{2}.0+1}=0$