Question

If sin(θ) = − 12/15 with θ in Quadrant IV, what is cos(θ)?

Answer 1

`costheta = 9/15`

Explanation:

Recall that

`sintheta + cos^2theta = 1`.

Therefore

`(-12/15)^2 + cos^2theta = 1`

`cos^2theta = 1 - 144/225`

`costheta = +-sqrt(81/225)`

`costheta = +- 9/15`

But since we're in the 4th quadrant, cosine is positive, therefore `costheta = 9/15`.

Hopefully this helps!