Question

若向量a的绝对值=3向量b的绝对值=2,且a与b的夹角为60度,则a-b的绝对值=

Answer 1

(a-b)^2=a^2-2a*b+b^2

=3^2-2*3*2*cos(60)+2^2

=7

故|a-b|=√7