When x

When x < At 0, there is ∫ (1/x) dx = ln (-x)+c; (x & lt0);

Therefore, regardless of x>0 or X.

In practice, the formula ∫( 1/x)dx=lnx+c is often used because it is simple and clear.

Just remember: x

Indefinite integral formula

1, ∫ a dx = ax+C, a and c are constants.

2. ∫ x a dx = [x (a+1)]/(a+1)+c, where a is a constant and a≦- 1.

3、∫ 1/x dx = ln|x| + C

4.∫ a x dx = (1/lna) a x+c, where a >；; 0 and 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