Trigonometry help ! !

[draotic]

1. The problem statement, all variables and given/known data
will sum1 prove this ........@=theta
1-cos@ / sin@ = tan(@/2)


2. Relevant equations



3. The attempt at a solution
i tried to do this
cos@ = cos^2(@/2) - sin^2 (@/2)
wat now?
...
thats doesnt get me anywhere

[Mentallic]

Since you have a half angle on the right side, you'll want to convert all angles into their half angle equivalents. For example, \sin(2x)=2\sin(x)\cos(x) therefore \sin(\theta)=2\sin\left(\frac{\theta}{2}\right) \cos \left(\frac{\theta}{2}\right)