Question

在△ABC中,C=90°,CB=3,点M满足向量BM=2MA,则

Answer 1

由于 CA*CB=0 ,

且 CM=CB+BM=CB+2/3*BA=CB+2/3*(CA-CB)=2/3*CA+1/3*CB ,

因此 CM*CB=2/3*CA*CB+1/3*CB^2=0+1/3*9=3 .