1. ## Differentiation Question

Let y = 1 - cos x / 1 + cosx

Show that dy/dx = t+t^3 , where t = tan(x/2)

2. ## Re: Differentiation Question

Probably easiest to get y in terms of half x right away, using

$\cos(2x) \equiv \cos^2 x - \sin^2 x$

i.e. $\displaystyle{\cos(x) \equiv \cos^2 \frac{x}{2} - \sin^2 \frac{x}{2}\displaystyle{$

Then simplify using Pythag,

$\cos^2 x + \sin^2 x \equiv 1$

3. ## Re: Differentiation Question

Its it possible that you mean (1- cos(x))/(1+ cos(x))?