赞 JACK511 幼苗
共回答了21个问题采纳率：95.2% 举报
π/2cos(a/2)
tan(a/2)-cos(a/2)
sin(a/2)+cos(a/2)>0
原式=sin(a/2)+cos(a/2)-(sin(a/2)-cos(a/2))-2cos(a/2)-2sin(a/2)
=2cos(a/2)-2cos(a/2)-2sin(a/2)
=-2sin(a/2)
tan(a/2)-cos(a/2)
sin(a/2)+cos(a/2)>0
原式=sin(a/2)+cos(a/2)-(sin(a/2)-cos(a/2))-2cos(a/2)-2sin(a/2)
=2cos(a/2)-2cos(a/2)-2sin(a/2)
=-2sin(a/2)
1年前 追问
8
对，带括号 sin(a/2)+cos(a/2)>0 sin(a/2)-cos(a/2)>0 [sin(a/2)+cos(a/2)]^2=1+sina [sin(a/2)-cos(a/2)]^2=1-sina 1+cosa=2cos(a/2)^2 1-cosa=2sin(a/2)^2 =|sin(a/2)+cos(a/2)|-|sin(a/2)-cos(a/2)|+2|cos(a/2|-2|sin(a/2| =sin(a/2)+cos(a/2)- (sin(a/2)-cos(a/2)）-2cos(a/2)-2sin(a/2) =2cos(a/2)-2cos(a/2)-2sin(a/2) =-2sin(a/2)
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