trig finding the exact value

Question

find the exact value of sin(u-v) given that sin u=3/5, and sin v=4/5.

find the exact value of cos(u+v) given that sin u=4/5, and sin v=5/13.

Answer 1

Assuming that u and v are acute, sinu = 3/5 and cosu = 4/5

sinv = 5/13 and cosv = 12/13

cos(u+v) = cosucosv - sinusinv = (4/5)(12/13) - (3/5)(5/13) = 48/65 - 15/65 = 33/65

Answer 2

sinu=.6; u=36.87

"v=.8; v=30

"6.87=.1196

sinu=.8; u=53.13

"v=.384; v=22.62

cos75.75=.246