解:
1、sinx+cosx=√2(sinx*√2/2+cosx*√2)
因為cosx=√2/2,sinx=√2/2
所以sinx+cosx=√2(sinxcosπ/4+cosxsinπ/4)=√2sin(x+π/4)
2、sinx+cosx
=√2(√2/2 * sinx+√2/2 * cosx)
=√2(sinxcos45度+cosxsin45度)
=√2sin(x+45度