Question

一道空间向量的填空提...已知OABC是四面体,M,N分别是OA,BC的中点,点G在MN上且MG=2/3MN,若OG=x

Answer 1

OG=ON+NG=(OB+OC)/2+NM/3=(OB+OC)/2+(NA+AM)/3=(OB+OC)/2+(OA-ON+AM)/3=

(OB+OC)/2+(OA-(OB+OC)/2-OA/2)/3=OA/6+OB/3+OC/3