y:=e^(-x)*sin (x);
int (y, x, 0, infinity);
int (e^(-x)*sin (x), x, 0, infinity);
y;
df (y, x);
int (y, x);
g:=ws;
gup:=limit (g, x, infinity);
glw:=sub (x=0, g);
f:=gup-glw;
end;