法一：sin（x+π/4）=sinxcosπ/4+cosxsinπ/4=√2/2(sinx+cosx)cos(x-π/4)=cosxcosπ/4+sinxsinπ/4=√2/2(sinx+cosx)所以相等.法二：sin（x+π/4）=sin(x+π/2-π/4）=sin[π/2-(π/4-x)]=cos(π/4-x)=cos(x-π/4...