Trigonometry Identities

Question

Suppose that cosm=−3/10 and that m is in the third quadrant. What is the value of tanm?

Answer 1

1 + tan^2 m = 1 / cos^2 m

tan^2 m = 1 / (-0.3)^2 - 1 = 91/9

tan m = sqrt(91/9) (positive for Q3)