Question

$L{t}_{h\to 0}\frac{{\cos }^2\left(x+h\right)-{\cos }^{2}x}{h}$ is equal to

• A. ${\cos }^{2}x$
• B. - sin 2x
• C. sin x cos x
• D. 2 sin x

Answer 1

Answer: (B)

The given limit $=\frac{d}{dx}({\cos }^{2}x)$
$=-2\cos x\sin x=-\sin 2x$.