Školjka

%V0 Ako za kutove trokuta $\alpha$ i $\beta$ vrijedi relacija $$ \sin^2 \left(\dfrac{\alpha}{2}\right) \cdot \cos^3 \left(\dfrac{\beta}{2}\right) = \sin^2 \left(\dfrac{\beta}{2}\right) \cdot \cos^3 \left(\dfrac{\alpha}{2}\right), $$ dokaži da je $\alpha=\beta$.