Question

Найдите косинус угла между векторами

Answer 1

$overrightarrow {A}+overrightarrow {B}=(2+0; 0-1; 1+1) = (2; -1; 2) \ overrightarrow {A}-overrightarrow {B}=(2-0; 0+1; 1-1) = (2; 1; 0) \ cos alpha = frac {x_1x_2+y_1y_2+z_1z_2}{sqrt{x_1^2+y_1^2+z_1^2} cdot sqrt{x_2^2+y_2^2+z_2^2}} = \ = frac {(2)(2)+(-1)(1)+(2)(0)}{sqrt{(2)^2+(-1)^2+(2)^2} cdot sqrt{(2)^2+(1)^2+(0)^2}} = \ = frac {1}{sqrt{5}}$

Answer 2

Спасибо! :)

Answer 3

На здоровье