Answer
$x^{2}$+$y^{2}$=$sin^{2}$($\frac{\theta}{2}$)+$cos^{2}$($\frac{\theta}{2}$)=1 For −$\pi$ ≤ $\theta$ ≤ $\pi$
Work Step by Step
a.
$x=\sin(\frac{\theta}{2}$)....(1)
$y=\cos(\frac{\theta}{2}$)....(2)
by squaring and summing both (1) and (2)
$x^{2}+y^{2}=\sin^{2}(\frac{\theta}{2})+\cos^{2}(\frac{\theta}{2})=1$ for −$\pi \leq \theta \leq \pi$
