Se foloseste formula:
[tex]sin\dfrac{\alpha}{2}=\pm\sqrt{\dfrac{1-cos\alpha}{2}}[/tex] in care luam semnu "+" in fata radicalului, deoarece in primul cadran sin este pozitiv.
Deci:
[tex]sin22^{\circ}\ 30'=\sqrt{\dfrac{1-cos45^{\circ}}{2}}=\sqrt{\dfrac{1-\frac{\sqrt2}{2}}{2}}=\dfrac{\sqrt{2-\sqrt2}}{2}[/tex]
