$\sin {20}^o=\frac{20}{c}$

$c=\frac{20}{\sin {20}^o}$   

 

$\cos {20}^o=\frac{x}{c}$  

$c=\frac{x}{\cos {20}^o}$  

 

Stąd:

$\frac{20}{\sin {20}^o}=\frac{x}{\cos {20}^o}$   

$\frac{20}{\sin {20}^o}\cdot \cos {20}^o=x$  

$\frac{20}{\sin {20}^o}\cdot \frac{1}{\frac{1}{\cos {20}^o}}=x$  

$x=\frac{20}{\frac{\sin {20}^o}{\cos {20}^o}}$  

$x=\frac{20}{\mathrm{tg}{20}^o}\left[\text{m}\right]$  

Odpowiedź A