Question

Verify the identity. tan (x + pi/2) = -cot x

Answer 1

$\tan\left(x+\dfrac\pi2\right)=\dfrac{\sin\left(x+\frac\pi2\right)}{\cos\left(x+\frac\pi2\right)}=\dfrac{\sin x\cos\frac\pi2+\cos x\sin\frac\pi2}{\cos x\cos\frac\pi2-\sin x\sin\frac\pi2}=\dfrac{\cos x}{-\sin x}=-\cot x$