Question

How do you find the exact value of `sin(u+v)` given that `sinu=-7/25` and `cosv=-4/5`?

Answer 1

Question undefined

Explanation:

Use trig identity:
sin (u + v) = sin u.cos v + sin v.cos u
We know: `sin u = -7/25` and `cos v = - 4/5`. Find cos u and sin v.
`cos^2 u = 1 - sin^2 u = 1 - 49/625 = 576/625` --> `cos u = +- 24/25`
We can't determine cos u because we don't know which Quadrant angle u is in.
The same problem with sin v.