已知tanx=2，求2sin2x-sinxcosx+cos2x的值．
问题描述：
已知tanx=2，求2sin2x-sinxcosx+cos2x的值．
答
=
=
=
．
∵tanx=2，
∴2sin2x-sinxcosx+cos2x
=
| 2sin2x−sinxcosx+cos2x |
| sin2x+cos2x |
=
| 2tan2x−tanx+1 |
| tan2x+1 |
=
| 8−2+1 |
| 4+1 |
=
| 7 |
| 5 |