Пошаговое объяснение:
a*b = |a| * |b| * cosa
a*b = ax * bx + ay * by + az * bz = (-3)*1 + 0*(-2) + 4*2 = 5
|a| = √(ax^2 + ay^2 + az^2) = √(9 + 0 + 16) = 5
|b| = √(bx^2 + by^2 + bz^2) = √(1 + 4 + 4) = 3
cosa = (a*b)/(|a| * |b|) = 5/(5*3) = 1/3
