BC через векторы a=AK и b=BM
Решение.
По правилу треугольника
vector{АК}+vector{КC}=vector{AC}
и
vector{BM}+vector{MC}=vector{BC} ⇒ (т.к. vector{MC}=(1/2)vector{АC}
vector{BC}=vector{b}+(1/2)*vector{AC}=
=vector{b}+(1/2)vector{АК}+(1/2)vector{КC}=
=vector{b}+(1/2)vector{a}+(1/2)*(1/2) vector{BC}.
Итак,
vector{BC}=vector{b}+(1/2)vector{a}+(1/2)*(1/2) vector{BC}.
(3/4)vector{BC}=vector{b}+(1/2)vector{a}
vector{BC}=(4/3)*vector{b}+(4/3)*(1/2)vector{a}