∫ 1/sin^4(x) dx= ∫ csc^4(x) dx= ∫ csc^2(x)[csc^2(x) dx]= ∫ (1 + cot^2(x)) d(- cot(x))= - cot(x) - (1/3)cot^3(x) + C利用1 + cot^2(x) = csc^2(x)以及∫ csc^2(x) dx = - cot(x)