cosX+sinX=根号2sin(X+π/4）是怎么推出来的,
问题描述：
cosX+sinX=根号2sin(X+π/4）是怎么推出来的,
答
f(x)=cosx+sinx=√2(√2/2cosx+√2/2sinx)=√2(sin45cosx+cos45sinx)=√2sin(45+x)
答
sinx+cosx
=√2(√2/2*sinx+√2/2cosx)
=√2(sinxcosπ/4+cosxsinπ/4)
=√2sin(x+π/4)