Question

已知向量a,b满足|a|=1|b|=3,a与b的夹角为60度,则a*(a+b)=

Answer 1

a*(a+b)=a*a+a*b = |a|^2 + |a|*|b|*cos(a与b的夹角) = 1^2 + 1*3*cos(60) = 1 + 3*(1/2) = 5/2