Solution 4.3:3e
From Förberedande kurs i matematik 1
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| - | The angle   | + | The angle <math>\pi/2+v</math> 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 <math>\pi/2+v</math> is equal to the ''y''-coordinate for ''v'', but with a change of sign, i.e.  | 
| - | <math>  | + | |
| - | makes the same angle with the positive   | + | |
| - | + | ||
| - | -axis as the angle   | + | |
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| - | makes with the positive   | + | |
| - | + | ||
| - | -axis, and hence we see that the   | + | |
| - | + | ||
| - | -coordinate for   | + | |
| - | <math>  | + | |
| - | is equal to the   | + | |
| - | + | ||
| - | -coordinate for   | + | |
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| + | {{Displayed math||<math>\cos \Bigl(\frac{\pi}{2}+v\Bigr) = -\sin v = -a\,\textrm{.}</math>}}  | ||
| - | + | {| align="center"  | |
| - | + | |align="center"|[[Image:4_3_3_e-1.gif|center]]  | |
| - | [[Image:4_3_3_e-1.gif|center]][[Image:4_3_3_e-2.gif|center]]  | + | |align="center"|[[Image:4_3_3_e-2.gif|center]]  | 
| - | + | |-  | |
| - | + | |align="center"|<small>Angle ''v''</small>  | |
| - | + | |align="center"|<small>Angle π/2 + ''v''</small>  | |
| - | <  | + | |}  | 
| - | + | ||
| - | <  | + | |
Current revision
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.
| \displaystyle \cos \Bigl(\frac{\pi}{2}+v\Bigr) = -\sin v = -a\,\textrm{.} | 
| Angle v | Angle π/2 + v | 


