∫[0,π/2](sint)^ndt=∫[0,π/2]sint^(n-1)d(-cost)= -sint^(n-1)cost|[0,π/2]+∫[0,π/2]cost^2*(n-1)sint^(n-2)dt=∫[0,π/2](1-sint^2)*(n-1)sint^(n-2)dt=∫[0,π/2](n-1)sint^(n-2)dt - (n-1)∫[0,π/2](sint...