lmlylb
幼苗
共回答了24个问题采纳率：95.8% 举报
sin²x-cos²x>cosx-sinx
即（sinx+cosx)(sinx-cosx)+(sinx-cosx)>0
(sinx-cosx)(sinx+cosx+1)>0
（sinx-cosx)[√2(√2/2sinx+√2/2cosx)+1]>0
(sinx-cosx)[√2sin(x+π/4)+1]>0
∴sinx-cosx>0且sin(x+π/4)>-√2/2 ①
或sinx-cosx sinx>cosx
==> π/4 π/4
1年前
3
