| sinα•cosβ+cosα•sinβ−2sinα•cosβ |
| 2sinα•sinβ+cosα•cosβ−sinα•sinβ |
=
| −(sinα•cosβ−cosα•sinβ) |
| cosα•cosβ+sinα•sinβ |
=-
| sin(α−β) |
| cos(α−β) |
（2）原式=
| (1+tanθ)−(1−tanθ) |
| 1−tan2θ |
=
| 2tanθ |
| 1−tan2θ |
| sin(α+β)−2sinαcosβ |
| 2sinαsinβ+cos(α+β) |
| 1 |
| 1−tanθ |
| 1 |
| 1+tanθ |
| sinα•cosβ+cosα•sinβ−2sinα•cosβ |
| 2sinα•sinβ+cosα•cosβ−sinα•sinβ |
| −(sinα•cosβ−cosα•sinβ) |
| cosα•cosβ+sinα•sinβ |
| sin(α−β) |
| cos(α−β) |
| (1+tanθ)−(1−tanθ) |
| 1−tan2θ |
| 2tanθ |
| 1−tan2θ |