> int( sin(x), x );

-cos(x)

> smittel=1/T*(int (U, s=(-a*T/2)..(a*T/2)));

smittel = U*a

> cn=1/T*(int (U*exp(-I*n*w*t), t=(-a*T/2)..(a*T/2)));

cn = I*U*(exp(-1/2*I*n*w*a*T)-exp(1/2*I*n*w*a*T))/(...

> an=1/T*(int (U*cos(n*w*t), t=(-a*T/2)..(a*T/2)));

an = 2*U*sin(1/2*n*w*a*T)/(T*n*w)

> bn=1/T*(int (U*sin(n*w*t), t=(-a*T/2)..(a*T/2)));

bn = 0

> convert(sin(p),exp);

-1/2*I*(exp(I*p)-1/exp(I*p))

>