supplementary angles

Im having trouble figuring out problems with supplementary angles. I know that if you have cos^2(x) + sin^2(y) where x+y = 180 then cos^2(x) + sin^2(y) = 1. But what is sin(t) in terms of cosine and vice versa? What I mean is sin(t) = cos(?). I was looking back on a problem, how would I solve cos(10)sin(70) + sin(20)sin(190)?