已知向0,量a=(cos*(5x/3),sin(5x/3)),b=(cos(x/3),-sin(x/3))x属于[

问题描述:

已知向0,量a=(cos*(5x/3),sin(5x/3)),b=(cos(x/3),-sin(x/3))x属于[
已知向量a=(cos*(5x/3),sin(5x/3)),b=(cos(x/3),-sin(x/3))x属于[0,派/2]
1 求a*b 及绝对值a+b
2若f(x)=a*b-2λ绝对值a+b,(λ>0)的最小值为-2/3求λ

a*b=cos*(5x/3) * cos(x/3) - sin(5x/3)sin(x/3)=cos(5x/3+x/3)=cos2x
a+b=sqr(a平方+b平方+2ab)