Lösung 4.3:3e
Aus Online Mathematik Brückenkurs 1
The angle \displaystyle \pi/2+v makes the same angle with the positive y-axis as the angle v makes with the positive x-axis, and hence we see that the x-coordinate for \displaystyle \pi/2+v is equal to the y-coordinate for v, but with a change of sign, i.e.
 |  |
| Angle v | Angle π/2 + v |
