Solution 4.2:3b
From Förberedande kurs i matematik 1
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| - | The angle   | + | The angle <math>2\pi</math> corresponds to a whole revolution and therefore we see that if we draw in a line with angle <math>2\pi</math> relative to the positive ''x''-axis, we will get the positive ''x''-axis.  | 
| - | <math>  | + | |
| - | corresponds to a whole revolution and therefore we see that if we draw in a line with angle   | + | |
| - | <math>  | + | |
| - | relative to the positive   | + | |
| - | + | ||
| - | -axis, we will get the positive   | + | |
| - | + | ||
| - | -axis.  | + | |
[[Image:4_2_3_b.gif|center]]  | [[Image:4_2_3_b.gif|center]]  | ||
| - | Because   | + | Because <math>\cos 2\pi</math> is the ''x''-coordinate for the point of intersection between the line with angle <math>2\pi</math> and the unit circle, we can see directly that <math>\cos 2\pi = 1\,</math>.  | 
| - | <math>\cos   | + | |
| - | is the   | + | |
| - | + | ||
| - | -coordinate for the point of intersection between the line with angle   | + | |
| - | <math>  | + | |
| - | and the unit circle, we can see directly that  | + | |
| - | <math>\cos   | + | |
Current revision
The angle \displaystyle 2\pi corresponds to a whole revolution and therefore we see that if we draw in a line with angle \displaystyle 2\pi relative to the positive x-axis, we will get the positive x-axis.
Because \displaystyle \cos 2\pi is the x-coordinate for the point of intersection between the line with angle \displaystyle 2\pi and the unit circle, we can see directly that \displaystyle \cos 2\pi = 1\,.

