# How do you find the coordinates of the terminal points corresponding to the following arc length on the unit circle: 4π/3?

##### 1 Answer
May 21, 2015

Use the trig unit circle as proof. The coordinates of the arc's terminal point are:

$x = \cos \frac{4 \pi}{3} = \cos \left(\frac{\pi}{3} + \pi\right) = - \cos \left(\frac{\pi}{3}\right) = - \frac{1}{2}$ (Quadrant III)

$y = \sin \left(\frac{4 \pi}{3}\right) = \sin \left(\frac{\pi}{3} + \pi\right) = - \sin \left(\frac{\pi}{3}\right) = \frac{- \sqrt{3}}{2}$-