Question

If 90 degrees < theta < 180 degrees, and cos theta = 5/7, what is the cos (-theta)?

I don’t have the mathematical inserts so degrees and theta would of course be used with their actual sign. Thank you in advanced

Answer 1

-5/7

Explanation:

cos(-theta) = cos(theta)

cos(theta) = -5/7

(Because Quadrant 2)

cos(-theta) = -5/7