Let x = tanθ and dx = sec²θ dθ
∫ dx/(x²+1)^(3/2)
= ∫ (sec²θ)/(tan²θ+1)^(3/2) dθ
= ∫ (sec²θ)/(sec²θ)^(3/2) dθ
= ∫ (sec²θ)/(sec³θ) dθ
= ∫ cosθ dθ
= sinθ + C
= x/√(1+x²) + C
不定积分的公式
1、∫ a dx = ax + C,a和C都是常数
2、∫ x^a dx = [x^(a + 1)]/(a + 1) + C,其中a为常数且 a ≠ -1
3、∫ 1/x dx = ln|x| + C
4、∫ a^x dx = (1/lna)a^x + C,其中a > 0 且 a ≠ 1
5、∫ e^x dx = e^x + C
6、∫ cosx dx = sinx + C
7、∫ sinx dx = - cosx + C
8、∫ cotx dx = ln|sinx| + C = - ln|cscx| + C
超简单