## Trigonometry (10th Edition)

It could be found by finding the terminal angle of $\cos$ 2000$^{\circ}$, and then using that terminal angle to find the reference angle which would be significantly smaller, and could be used to evaluate the equation.
2000$^{\circ}$ - 5(360$^{\circ}$) = 200$^{\circ}$ 200$^{\circ}$ = The terminal angle of 2000$^{\circ}$ 180$^{\circ}$ - 200$^{\circ}$ = -20$^{\circ}$ -20$^{\circ}$ = The reference angle of 200$^{\circ}$ Therefore: $\cos$ 2000$^{\circ}$ = -$\cos$ 20$^{\circ}$ -$\cos$ 20$^{\circ}$ = -0.93969262