Chapter 3 - Section 3.5 - Derivatives of Trigonometric Functions - Exercises - Page 151: 22

$\displaystyle s' = \frac{-1}{(1-cost)}=\frac{1}{cost-1}$

$\displaystyle s = \frac{sint}{1-cost}$ $\displaystyle s' = \frac{(1-cost)cost - sin^{2}t}{(1-cost)^{2}}$ $\displaystyle s' = \frac{cost-cos^{2}t-sin^{2}t}{(1-cost)^{2}}$ $\displaystyle s' = \frac{cost-1}{(1-cost)^{2}}$ $\displaystyle s' = \frac{-1}{(1-cost)}$