Question

помогите срочно надо

Answer 1

$|bar{a}-bar{b}|^2 = |bar{a}|^2+|bar{b}|^2-2|bar{a}||bar{b}|cos(bar{a};bar{b}), \ |bar{a}+bar{b}|^2 = |bar{a}|^2+|bar{b}|^2+2|bar{a}||bar{b}|cos(bar{a};bar{b}), \ cos(bar{a};bar{b}) = frac{|bar{a}+bar{b}|^2-|bar{a}|^2-|bar{b}|^2}{2|bar{a}||bar{b}|}, \ |bar{a}-bar{b}|^2 = |bar{a}|^2+|bar{b}|^2-2|bar{a}||bar{b}|frac{|bar{a}+bar{b}|^2-|bar{a}|^2-|bar{b}|^2}{2|bar{a}||bar{b}|} = 2|bar{a}|^2+2|bar{b}|^2-|bar{a}+bar{b}|^2,$
$|bar{a}-bar{b}|^2 = 2cdot13^2+2cdot19^2-20^2 = 660, |bar{a}-bar{b}| = 2sqrt{165}.$