|sina-cosa|=|√2sin(a-π/4) | 这是为什么

问题描述:

|sina-cosa|=|√2sin(a-π/4) | 这是为什么

sina-cosa
=√2[(√2/2)sina-(√2/2)cosa]
=√2(sinacosπ/4-cosasinπ/4)
=√2sin(a-π/4)