题目内容

实数x,y满足tanx=x,tany=y,且|x|≠|y|,则
sin(x+y)
x+y
-
sin(x-y)
x-y
=______.
tanx=
sinx
cosx
=x
∴sinx=xcosx
同理,siny=ycosy
所以原式=
sinxcosy+cosxsiny
x+y
-
sinxcosy-cosxsiny
x-y

=
xcosxcosy-ycosxcosy
x-y
-
xcosxcosy+ycosxcosy
x+y

=
cosxcosy(x+y)
x+y
-
cosxcosy(x-y)
x-y

=cosxcosy-cosxcosy
=0
故答案为:0
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