Find the exact value of the trigonometric expression given that sin(u) = 21/ 29 and cos(v) = − 15 /17 . (Both u and v are in Quadrant II.)

Question

cos(v − u)

= _____________

Answer 1

By the Pythagorean Identity (handy to learn)

sin u 21 / 29 ⇒ cos u = 20 / 29

cos v = -15 / 17 ⇒ sin v = 8 / 17

Substitute values in appropriate formula and simplify.