The formula for calculating the center of mass in the double integral of the postgraduate entrance examination is ∫∫D xdxdy= the abscissa area of the center of gravity × d, ∫∫D ydxdy= the ordinate area of the center of gravity × d.

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