Цитата(dolgmax @ 30.11.2008, 9:00) *

e^x=t
тогда
-int(t^3dt/1+t^2)=-int(td(1+t^2)/2(1+t^2)=-t/2-ln(t^2+1)/2 +c

e^x=t;
e^xdx=dt;
-int(e^{3x}dx/(e^{2x}+1))=-int(t^2dt/(1+t^2))=int(dt/(1+t^2))-int(dt)=arctg(e^x)-e^x+C