Find the exact value of the trig function below.
cos(x+y) if sinx = , cosx = , siny = , and cosy =

cos (x+y)=cos x.cos y -sin x.sin y
Data:
sin x=12/13
cos x=5/13
sin y=8/17
cos y=15/17

therefore:
cos (x+y)=cos x.cos y -sin x.sin y
cos (x+y)=(5/13)(15/17)-(12/13)(8/17)
cos (x+y)=75/221-96/221
cos (x+y)=-21/221

 cos (x+y)=-21/221

We can check it out our
sin x=12/13
x=sin⁻¹(12/13)≈67.38

y=sin (8/17)≈28.07

(x+y)=67.38 + 28.07=95.45
(x+y)=cos⁻¹(-21/221)=95.45