y=1/2cos²x+sinxcosx+3/2sin²x
=1/2+sinxcosx+sin²x
=1/2+1/2sin2x+(1-cos2x)/2
=1/2sin2x-1/2cos2x+1
=√2/2sin(2x-π/4)+1第一步就看不懂= =y=1/2cos²x+sinxcosx+3/2sin²x=(1/2cos²x+1/2sin²x)+sinxcosx+sin²x=1/2+sinxcosx+sin²xcos²x+sin²x=1