Solution 4.3:8d
From Förberedande kurs i matematik 1
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| - | {{  | + | It seems natural to try to use the addition formula on the numerator of the left-hand side:  | 
| - | + | ||
| - | {  | + | |
| + | <math>\begin{align}  | ||
| + | & \frac{\cos \left( u+v \right)}{\cos u\cos v}=\frac{\cos u\centerdot \cos v-\sin u\centerdot \sin v}{\cos u\centerdot \cos v} \\   | ||
| + | & =1-\frac{\sin u\centerdot \sin v}{\cos u\centerdot \cos v}=1-\tan u\centerdot \tan v. \\   | ||
| + | \end{align}</math>  | ||
Revision as of 11:13, 30 September 2008
It seems natural to try to use the addition formula on the numerator of the left-hand side:
\displaystyle \begin{align}
& \frac{\cos \left( u+v \right)}{\cos u\cos v}=\frac{\cos u\centerdot \cos v-\sin u\centerdot \sin v}{\cos u\centerdot \cos v} \\ 
& =1-\frac{\sin u\centerdot \sin v}{\cos u\centerdot \cos v}=1-\tan u\centerdot \tan v. \\ 
\end{align}
