dxdy = xy - sin2 (y/x) Put y = vx ⇒ dxdy = v + x dxdv v + x dxdv = v - sin2 v ⇒ - csc2 v dv = xdx Integrating both sides, we get ∫csc2 v dv = ∫ xdx ⇒ cot v = log x + C cot xy = log x + C Curve passes through the point (1,4π) ∴ C = 1 ⇒ cot xy = log x + logee ⇒ cot xy = log xe ⇒ y = x cot−1 (loge ex)