Determine Sin(x+y)

If Sinx = 4/5 Cosy = 12/13

Therefore the following is true.

sinx = 4/5

cosx = (+/-)3/5

siny = (+/-)5/12

cosy = 12/13

Angle X can be in Quadrant 1 or 2

Angle Y can be in Quadrant 1 or 4

s(x+y) = (4/5)(12/3) + (3/5)(5/12)

= 63/65

My Question is, that is this the only solution or do i have to plug in the negative values of cosx and siny in the equation to get different answers?

Thanks Alot