(2*(cos240 ° +isin240))^4=2^4*(cos (240 ° *4)+isin(240 ° *4))=16*(cos960 ° +isin960 ° )
cos 960 ° =cos(5*180 ° +60 °)=-cos60 ° =-1/2
sin 960 ° =sin(5*180 ° +60 °)=-sin60 ° =-sqrt(3)/2
(2*(cos240 ° +isin240))^4=16*(cos960 ° +isin960 ° )=16*((-1/2)+i*(sqrt(3)/2))=[b]-8-i*8*sqrt(3)[/b]
∫ 2xsinxdx=2 ∫ xsinxdx
по частям
u=x
du=dx
dv=sinxdx
v= ∫ sinxdx=-cosx
=2*(-x*cosx- ∫ (-cosx)dx)=
=-2x*cosx-2 ∫ cosxdx=
=[b]-2x*cosx-2 *sinx + C[/b]