y=tan(x+y)arctany = x+y[1/(1+y^2)] dy/dx = 1+ dy/dxdy/dx =-(1/y^2) -1d^2y/dx^2 = (2/y^3)(dy/dx) =(2/y^3)(-(1/y^2) -1)=-2( 1/y^5 + 1/y^3 )
