若tan(α+ π 4 )=2,则sin 2 a+sinacosa=______

若tan(α+ π 4 )=2,则sin 2 a+sinacosa=______.
2025-06-22 17:08:42
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sin 2 a+sinacosa
=
sin 2 α+sinαcosα
sin 2 α+ cos 2 α 

=
tan 2 α+tanα
tan 2 α+1

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

故答案为:
2
5