Mathematics

Problem

Find

\dfrac{d}{dx}\left(\dfrac{x}{1-\cos x}\right)

for

x\neq0

. a)

\dfrac{1-\cos x+ x\sin x}{1-\cos x}

\dfrac{1-\cos x+ x\sin x}{(1-\cos x)^2}

\dfrac{1-\cos x- x\sin x}{(1-\cos x)^2}

\dfrac{1+ x\sin x}{1-\cos x}