Question

let sinx= 15/17, cosx<0, tany=-12/5 andy siny<0, find
sin(x+y)

Answer 1

i know that sin(x+y) = sinxcosy+cosxsiny
=15/17cosy + cosxsiny

Answer 2

15/17cosy + cosxsiny=cos y (15/17+cos x tan y)=cos y (15/17-12/5cos x)

so u just need to evaluate cos y and cos x

Answer 3

Find cos x = 8/17

Answer 4

use this identities
\[\sin^2 x+\cos^2 x=1\]\[1+\tan^2 y=\frac{1}{\cos^2 y}\]

Answer 5

draw your triangles...
for angle y, you have a negative tangent so so cosy will be postive....

Answer 6

cos x = -8/17 because cos x < 0

Answer 7

yes

Answer 8

do the same thing that @Yahoo! did with the other angle, angle y.....