Use the unit circle to find cos (-270°)

Question

asked May 19, 2020 62.8k views

2 Answers

Afshin Oroojlooy · Answer 1 · 2020-05-22T18:13:46+0000

Answer:

$\cos (-270\degree)=0$ .

Explanation:

We want to find the value of
$\cos (-270\degree)$ .

Note that;

$\cos (-\theta)=\cos (\theta)$

This implies that;

$\cos (-270\degree)=\cos (270 \degree)$

Also 270 degrees is a quadrantal angle.

On the unit circle,
$\cos (270\degree)$ is the x-coordinate of the point
(0,-1)

Hence,
$\cos (-270\degree)=0$ .