问题 解答题
若tan(π+x)=2,求:
(1)
4sinx-2cosx
5cosx+3sinx

(2)
sinxcosx
1+cos2x
答案

tan(π+x)=2,tanx=2,

(1)

4sinx-2cosx
5cosx+3sinx
=
4tanx-2
5+3tanx
=
4×2-2
5+3×2
=
5
7

(2)

sinxcosx
1+cos2x
=
tanx
2+tan2x
=
2
2+2×2
=
1
3

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