how do you find the exact value sin(x+y), sinx=
5
3
and \sec y=-\frac{13}{5}secy=−
5
13
geez - learn how to type fractions!
since sinx = 3/5, cosx = 4/5 (think of a 3-4-5 right triangle)
(you say that sinx = 5/3, but that is impossible)
since secy = 13/5, cosy = 5/13 and siny = 12/13 (5-12-13 triangle)
Now, review your addition formulas.
sin(x+y) = sinx cosy + cosx siny