Find the exact value ofcos (u+v) given that sin u= 7/25 and cos v=−12/13. (Both u and v are in Quadrant II.)

Answer 1

since y>0 and x<0, draw your triangles, and you can see that

cos u = -24/25
sin v = 5/13

Now just plug them into your cos(u+v) formula.

Answer 2

so I got cos(u+v)=204/325

is this correct?

Answer 3

Hmmm. I get

cosu*cosv - sinu*sinv
= (-24/25)(-12/13)-(7/25)(5/13)
= 288/325 - 35/325
= 253/325