∫cos(x)/sin^2(x)dx
d/dxsinx=cosx
所以∫cos(x)/sin^2(x)dx=-1/3sin^3(x)+C
∫（3x+2)^2+(1/(3x+2)^2)dx
=6x+4-1/9(3x+2)^3+C
∫3sin(2x+1)+4/(2x+1)dx
=[3cos(2x+1)]/2+2ln(2x+1)+C
∫x(x^2+1)^(2/3)dx
因为d/dx(x^2)=2x
所以∫x(x^2+1)^(2/3)dx=[3(x^2+1)^(5/3)]/10+C
∫1/（x(x+1))dx
1/(x(x+1))=1/x-1/(x+1)
所以∫1/（x(x+1))dx=lnx+ln(x+1)+C