– bul formulalar tómendegishe boladı: $$\begin{array}{lll}\sin{\dfrac{\alpha}{2}}=\pm\sqrt{\dfrac{1-\cos\alpha}{2}}; & \cos{\dfrac{\alpha}{2}}=\pm\sqrt{\dfrac{1+\cos\alpha}{2}}; \\ [3mm] \text{tg}{\dfrac{\alpha}{2}}=\sqrt{\dfrac{1-\cos\alpha}{1+\cos\alpha}}; & \text{ctg}{\dfrac{\alpha}{2}}=\sqrt{\dfrac{1+\cos\alpha}{1-\cos\alpha}}.\end{array}$$