题目内容：

f(x)=sinx+cosx=根号2sin(x+pai/4) 是怎么样得来的呢?

优质解答

f(x) = sinx+cosx
= √2(sinx (1/√2) + cosx (1/√2) )
= √2(sinx cosπ/4 + cosx sinπ/4)
= √2(sin(x+π/4))