## Trigonometry (11th Edition) Clone

$d=r(1-\cos \frac{\theta}{2})$
Step 1: $d$ is the difference between $r$ and $h$. Step 2: $d=r-h$ Step 3: Since $h=r\cos \frac{\theta}{2}$, $d=r-h=r-(r\cos \frac{\theta}{2})=r(1-\cos \frac{\theta}{2})$