Solution 4.3:1a
From Förberedande kurs i matematik 1
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- | If we draw the angle | + | If we draw the angle <math>\pi/5</math> on the unit circle, then it will have an ''x''-coordinate that is equal to <math>\cos \pi/5\,</math>. |
- | <math> | + | |
- | on | + | |
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- | -coordinate that is equal to | + | |
- | <math> | + | |
- | . | + | |
- | + | [[Image:4_3_1_a.gif||center]] | |
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- | + | In the figures, we see also that the only other angle between <math>0</math> and <math>2\pi</math> which has the same cosine value, i.e. same ''x''-coordinate, is the angle <math>v=-\pi/5+2\pi = 9\pi/5</math> on the opposite side of the ''x''-axis. | |
- | In the figures, we see also that the only other angle between | + | |
- | <math>0</math> | + | |
- | and | + | |
- | <math>2\pi </math> | + | |
- | which has the same cosine value, i.e. same | + | |
- | + | ||
- | -coordinate, is the angle | + | |
- | <math>v=- | + | |
- | on the opposite side of the | + | |
- | + | ||
- | -axis. | + |
Current revision
If we draw the angle \displaystyle \pi/5 on the unit circle, then it will have an x-coordinate that is equal to \displaystyle \cos \pi/5\,.
In the figures, we see also that the only other angle between \displaystyle 0 and \displaystyle 2\pi which has the same cosine value, i.e. same x-coordinate, is the angle \displaystyle v=-\pi/5+2\pi = 9\pi/5 on the opposite side of the x-axis.