vector{AC}=vector{a}+vector{b}
vector{ОC}=(1/2)*vector{AC}=(1/2)*vector{a}+(1/2)*vector{b}
vector{АК}=(2/3)vector{а}
По правилу треугольника
vector{АК}+vector{КС}=vector{АС}
⇒ vector{КС}=vector{АС}-vector{АК}=
=(vector{a}+vector{b})-(2/3)vector{а}=
=(1/3)*vector{а}+vector{b}
vector{СК}=- vector{КС}=-(1/3)*vector{а}-vector{b}