tanα=1/2,求sinα−3cosαsinα+cosα=_.

问题描述:

tanα=

1
2
,求
sinα−3cosα
sinα+cosα
=______.

∵tanα=

1
2

sina−3cosa
sina+cosa
=
tanα−3
tanα+1
=
1
2
−3
1
2
+1
=-
5
3

故答案为:-
5
3