Question

已知tanθ=-2，则sinθcosθ的值为______．

Answer 1

由tanθ=-2，
则sinθcosθ=

sinθcosθ

sin2θ+cos2θ

=

1

tanθ+ 1 tanθ

=

1

-2- 1 2

=-

2

5

．
故答案为：-

2

5