f(x)
=a(2cos²x+2sinxcosx)+b
=a(cos2x+sin2x+1)+b
=√2asin(2x+π/4)+a+b
(1)当a=1时f(x)=√2sin(2x+π/4)+b+1
周期T=2π/2=π
-π/2+2kπ从 =a(cos2x+sin2x+1)+b怎么到=√2asin(2x+π/4)+a+b 这一步的