Solution 4.2:4f
From Förberedande kurs i matematik 1
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| - | {{  | + | If we add   | 
| - | <  | + | <math>2\pi </math>  | 
| - | {{  | + | to   | 
| + | <math>-\frac{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>-\frac{5\pi }{3}</math>  | ||
| + | and consequently has the same tangent value:  | ||
| + | |||
| + | |||
| + | <math>\begin{align}  | ||
| + | & \tan \left( -\frac{5\pi }{3} \right)=\tan \left( -\frac{5\pi }{3}+2\pi  \right)=\tan \frac{\pi }{3} \\   | ||
| + | & =\frac{\sin \frac{\pi }{3}}{\cos \frac{\pi }{3}}=\frac{\frac{\sqrt{3}}{2}}{\frac{1}{2}}=\sqrt{3} \\   | ||
| + | \end{align}</math>  | ||
Revision as of 13:27, 28 September 2008
If we add \displaystyle 2\pi to \displaystyle -\frac{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 -\frac{5\pi }{3} and consequently has the same tangent value:
\displaystyle \begin{align}
& \tan \left( -\frac{5\pi }{3} \right)=\tan \left( -\frac{5\pi }{3}+2\pi  \right)=\tan \frac{\pi }{3} \\ 
& =\frac{\sin \frac{\pi }{3}}{\cos \frac{\pi }{3}}=\frac{\frac{\sqrt{3}}{2}}{\frac{1}{2}}=\sqrt{3} \\ 
\end{align}
