I = ∫(sinx)^2/(cosx)^3 dx = ∫ secx (tanx)^2 dx = ∫ tanx d(secx) = secx tanx - ∫ (secx)^3 dx= secx tanx - ∫ [secx (tanx)^2 + secx] dx= secx tanx - I - ln|secx + tanx|I = (1/2) [secx tanx - ln|secx...