vector{AB}+vector{BD}=vector{AD}
vector{BD}=vector{AD}-vector{AB}=vector{b}-vector{a}
vector{OD}=(1/2)vector{BD}=(1/2)vector{b}-(1/2)vector{a}
б)
По правилу треугольника
vector{BС}+vector{СM}=vector{BM}
⇒
vector{BM}=vector{AD}-(1/2) vector{AB}=vector{b}-(1/2)vector{a}
По правилу треугольника
vector{AB}+vector{BM}=vector{AM} ⇒
vector{AM} =vector{a}+vector{b}-(1/2)vector{a}=vector{b}+(1/2)vector{a}
vector{MA} =-vector{AM} =-vector{b}-(1/2)vector{a}
в)
По правилу параллелограмма
vector{AB}+vector{AD}=vector{AC}
⇒
vector{AC}=vector{a}+vector{b}
vector{AO}=(1/2)vector{AC}
vector{OA}= - (1/2)vector{AC}= -(1/2)vector{a}-(1/2)vector{b}