已知向量a=(sinθ,根号3),向量b=(1,-cosθ),-π/2

题目

已知向量a=(sinθ,根号3),向量b=(1,-cosθ),-π/2

答案

a+b=(sinθ+1,√3-cosθ)
|a+b|^2=(sinθ+1)^2+(,√3-cosθ)^2
=5+2sinθ-2√3cosθ
=5+4sin(θ-π/6)
-π/2