1. dy=[sec(x+y)]^2*d(x+y) [cos(x+y)]^2*dy=dx+dy -[sin(x+y)]^2*dy=dx dy=-[csc(x+y)]^2*dx 2. d(y^2)=d(x+lny) 2ydy=dx+dy/y (2y-1/y)dy=dx dy=ydx/(2y^2-1)
