vector{a}*vector{b}=2*2+0*2+(-2)*(-4)=4+8=12
Длины векторов
|vector{a}|=sqrt(2^2+0^2+(-2)^2)=sqrt(8)=2sqrt(2)
|vector{b}|=sqrt(2^2+2^2+(-4)^2)=sqrt(24)=2sqrt(6)
cos ∠(vector{a},vector{b})=12/(2sqrt(2)*2sqrt(6))=sqrt(3)/2
∠(vector{a},vector{b})=[b]30 ° [/b]