Chapter 3 - Radian Measure and the Unit Circle - Section 3.2 Applications of Radian Measure - 3.2 Exercises - Page 109: 80

$d=(\frac{L}{\theta})(1-\cos \frac{\theta}{2})$

Substituting the answer from 77, $r=\frac{L}{\theta}$, into the answer of 79: $d=r(1-\cos \frac{\theta}{2})$ $d=(\frac{L}{\theta})(1-\cos \frac{\theta}{2})$ This is the formula that gives $d$ for specific values of $\theta$.