提问sin(π/4-θ)=1/3,则sin(π/4+θ)=

题目

提问sin(π/4-θ)=1/3,则sin(π/4+θ)=

答案

sin²(π/4-θ)+cos²(π/4-θ)=1
所以cos(π/4-θ)=±2√2/3
sin(π/4+θ)
=cos[π/2-(π/4+θ)]
=cos(π/4-θ)
=±2√2/3