Раскрываем скобки как в алгебре ( [i]векторная алгебра[/i])
= vector{a}* vector{a}- vector{b}* vector{a}+ vector{a}*2 vector{b}- vector{b}*2 vector{b}=
= vector{a}* vector{a}- vector{b}* vector{a}+2 vector{a}* vector{b}-2vector{b}*vector{b}=
по свойству скалярного произведения векторов: [r] vector{b}* vector{a}=vector{a}* vector{b} [/r]
= vector{a}* vector{a}+ vector{a}* vector{b}-2 vector{b}*vector{b}=
По определению скалярного произведения векторов: [r] vector{a}* vector{b}=|vector{a}|*| vector{b}|*cos ∠( vector{a}^ vector{b}) [/r]
=|vector{a}|*| vector{a}|*cos0 ° + |vector{a}|* |vector{b}|*cos 60 ° -2 |vector{b}|*|vector{b}}*cos0 ° =
=1*1*1+1*2*(1/2)-2*2*2*1=1+1-8=[b]-6[/b]