Question

Is it -56/65????????????????

Answer 1

Explanation:

-0.8615

Answer 2

`\cos (u + v) = -(56)/(65)`

Good job!

Explanation:

`\cos (u + v) = \cos u \cos v - \sin u \sin v`

`\sin u = -(3)/(5)`; u is in QIII.

That makes
`\cos u = -(4)/(5)`

`\sin v = -(12)/(13)`; v is in QIV.

That makes
`\cos v = (5)/(13)`

`\cos (u + v) = (-(4)/(5))((5)/(13)) - (-(3)/(5))(-(12)/(13))`

`\cos (u + v) = -(20)/(65) - (36)/(65)`

`\cos (u + v) = -(56)/(65)`

You are correct.