Найти угол между векторами а = (2; -2; 1) в = (-4; 1; 1)

Cosx = (ab) / (|a| * |b|)

cosx = (2 * (-4) + (-2) * 1+1*1) / (coren (2^2 + (-2) ^2+1^2) (c0ren (-4) ^2+1^2+1^2)) =

=-9 / (coren9 * coren18) = - 9/) 3*3coren2) = - 1/coren2

x=pi-pi/4=3pi/4