Solution 4.2:4f
From Förberedande kurs i matematik 1
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| - | {{  | + | If we add <math>2\pi</math> to <math>-5\pi/3\,</math>, we get a new angle in the first quadrant which corresponds to the same point on the unit circle  as the old angle <math>-5\pi/3</math> and consequently has the same tangent value,  | 
| - | + | ||
| - | + | {{Displayed math||<math>\begin{align}  | |
| + | \tan\Bigl(-\frac{5\pi}{3}\Bigr)  | ||
| + | = \tan\Bigl(-\frac{5\pi}{3}+2\pi\Bigr)  | ||
| + | = \tan\frac{\pi}{3}   | ||
| + | = \frac{\sin\dfrac{\pi}{3}}{\cos\dfrac{\pi}{3}}  | ||
| + | = \frac{\dfrac{\sqrt{3}}{2}}{\dfrac{1}{2}}  | ||
| + | = \sqrt{3}\,\textrm{.}  | ||
| + | \end{align}</math>}}  | ||
Current revision
If we add \displaystyle 2\pi to \displaystyle -5\pi/3\,, we get a new angle in the first quadrant which corresponds to the same point on the unit circle as the old angle \displaystyle -5\pi/3 and consequently has the same tangent value,
| \displaystyle \begin{align}
 \tan\Bigl(-\frac{5\pi}{3}\Bigr) = \tan\Bigl(-\frac{5\pi}{3}+2\pi\Bigr) = \tan\frac{\pi}{3} = \frac{\sin\dfrac{\pi}{3}}{\cos\dfrac{\pi}{3}} = \frac{\dfrac{\sqrt{3}}{2}}{\dfrac{1}{2}} = \sqrt{3}\,\textrm{.} \end{align}  | 
