Question

Integrala din xcosx............

Answer 1

$\int\limit {xcosx} \, dx=xsinx- \int\limits{sinx} \, dx=xsinx+cosx+C$
am utilizat formula de integrare prin parti (∫udv=uv-∫vdu)
am notat u=x,du=dx
              dv=cosxdx,v=sinx

Answer 2

$[tex]\int\limits x (sinx)' \, dx = xsinx - \int\limits (x)' sin x \, dx = xsinx - \int\limits sin x \, dx=$ [/tex]
$= xsinx - (-cos x) =xsinx+cosx +C$