Find the exact value of sin 2u,cos 2u, and tan 2 using double-angle formulas.

Question

Find the exact value of sin 2u,cos 2u, and tan 2uusing double-angle formulas. sec u = -2, pi/2 < u < pi

Answer 1

cosu = 1/secu = 1/(- 2) = - 1/2; u = 120°; sin2u = sin240° = - sin60° = - √3/2; cos2u = cos240° = - 1/2;

tan2u = tan240° = tan60° = √3.