Pokaži da za svaki trokut s kutovima
![\alpha](/media/m/f/c/3/fc35d340e96ae7906bf381cae06e4d59.png)
,
![\beta](/media/m/c/e/f/cef1e3bcf491ef3475085d09fd7d291e.png)
i
![\gamma](/media/m/2/4/a/24aca7af13a8211060a900a49ef999e9.png)
te polumjerima
![r](/media/m/3/d/f/3df7cc5bbfb7b3948b16db0d40571068.png)
i
![R](/media/m/4/d/7/4d76ce566584cfe8ff88e5f3e8b8e823.png)
upisane i opisane kružnice redom, vrijedi jednakost
%V0
Pokaži da za svaki trokut s kutovima $\alpha$, $\beta$ i $\gamma$ te polumjerima $r$ i $R$ upisane i opisane kružnice redom, vrijedi jednakost $$
\dfrac{\ctg\dfrac{\alpha}{2}+\ctg\dfrac{\beta}{2}}
{\ctg\dfrac{\gamma}{2}}=\dfrac{4R\sin^2\dfrac{\gamma}{2}}{r}.
$$