Općinsko natjecanje 2007 SŠ3 2
Dodao/la:
arhiva2. travnja 2012. Za kutove
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,
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,
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trokuta
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vrijedi

Dokaži da je trokut pravokutan.
%V0
Za kutove $\alpha$, $\beta$, $\gamma$ trokuta $ABC$ vrijedi $$
\cos^2\alpha+\cos^2\beta+\cos^2\gamma=1.
$$
Dokaži da je trokut pravokutan.
Izvor: Općinsko natjecanje iz matematike 2007