Question

Find the derivative of function $y=x\cos x$.

• A. $\cos x-x\sin x$
• B. $\cos x-\sin x$
• C. $x\cos x-\sin x$
• D. None of the above

Answer 1

The correct option is A $\cos x-x\sin x$

$y=x\cos x$

Using chain rule,
$\frac{dy}{dx}=\cos x+x(-\sin x)$
$\frac{dy}{dx}=\cos x-x\sin x$