∫x^3/√(1-x^2) dxletx= sinydx = cosydy∫x^3/√(1-x^2) dx= ∫(siny)^3 dy= -∫(siny)^2 dcosy= -∫[1-(cosy)^2] dcosy= (cosy)^3/3 - cosy + C=(1/3) (1-x^2)^(3/2) -(1-x^2)^(1/2) + C