若tan(α+π4)=2,则sin2a+sinacosa=______

若tan(α+π4)=2,则sin2a+sinacosa=______.
2025-06-22 09:54:15
推荐回答(1个)
回答1:

由tan(α+

π
4
)=
tanα+tan
π
4
1?tanαtan
π
4
=
tanα+1
1?tanα
=2,
解得:tanα=
1
3

则sin2a+sinacosa
=
sin2α+sinαcosα
sin2α+cos2α 

=
tan2α+tanα
tan2α+1

=
(
1
3
)
2
+
1
3
(
1
3
)
2
+1
=
2
5

故答案为:
2
5