Find the exact values (precalc)

Question

Find the exact values (fractions) for the trigonometric expression given that sin u = 4/5 and cos v = -7/25 (both u and v are in II quadrant)

Answer 1

u has a 3-4-5 right triangle, v has a 7-24-25 right triangle

cosu =-3/5, sin u=4/5. cosv=-7/25 sinv = 24/25

plug those values into sum or difference formulas to find sin(u+v), sin(u-v), cos(u+v) or cos(u-v)

or use a calculator with inverse trig functions to find angles u and v, and the sines or cosines of the sum or difference of those two angles.