2倍角公式
cos2x=cos²x-sin²x=1-2sin²x 2sin²x=1-cos2x
sin2x=2sinxcosx
y=2sin²x+2sinxcosx
=1-cos2x+sin2x
=sin2x-cos2x+1
=√2(√2/2sin2x-√2/2cos2x)+1
=√2(cosπ/4sin2x-sinπ/4cos2x)+1
=√2sin(2x-π/4)+1
T=2π/2=π
最小正周期π
2倍角公式
cos2x=cos²x-sin²x=1-2sin²x 2sin²x=1-cos2x
sin2x=2sinxcosx
y=2sin²x+2sinxcosx
=1-cos2x+sin2x
=sin2x-cos2x+1
=√2(√2/2sin2x-√2/2cos2x)+1
=√2(cosπ/4sin2x-sinπ/4cos2x)+1
=√2sin(2x-π/4)+1
T=2π/2=π
最小正周期π