问题 填空题
lim
x→
π
4
tan2x
cot(x-
π
4
)
=______.
答案

lim
x→
π
4
tan2x
cot(x-
π
4
)
=
lim
x→
π
4
2
2
sin2x(sinx-cosx)
2
2
cos2x( cosx+ sinx)
=
lim
x→
π
4
(- 
sin2x
1+sin2x
)
=-
sin
π
2
1+sin
π
2
=-
1
2

故答案为:-

1
2

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