cos(α+β)=5/13,sin(α+β)= -12/13
cosαcosβ-sinαsinβ=5/13
-√(1-x^2)*y-x*sinβ=5/13
sinαcosβ+cosαsinβ= -12/13
x*y-√(1-x^2)sinβ=-12/13
-√(1-x^2)*y-x*(x*y+12/13)/√(1-x^2)=5/13
y=-12/13-5/13*√(1-x^2)