[tex]sin\left(\cfrac{\theta}{2}\right)=\pm \sqrt{\cfrac{1-cos(\theta)}{2}} \qquad cos\left(\cfrac{\theta}{2}\right)=\pm \sqrt{\cfrac{1+cos(\theta)}{2}} \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ sin\left( \cfrac{30^o}{2} \right)\implies \sqrt{\cfrac{1-cos(30^o)}{2}}\implies \sqrt{\cfrac{1-\frac{\sqrt{3}}{2}}{2}}\implies \sqrt{\cfrac{~~\frac{2-\sqrt{3}}{2}~~}{2}}[/tex]
[tex]\sqrt{\cfrac{2-\sqrt{3}}{2}\cdot \cfrac{1}{2}}\implies \sqrt{\cfrac{2-\sqrt{3}}{4}}\implies \boxed{\cfrac{\sqrt{2-\sqrt{3}}}{2}} \\\\[-0.35em] ~\dotfill\\\\ cos\left( \cfrac{30^o}{2} \right)\implies \sqrt{\cfrac{1+cos(30^o)}{2}}\implies \sqrt{\cfrac{1+\frac{\sqrt{3}}{2}}{2}}\implies \sqrt{\cfrac{~~\frac{2+\sqrt{3}}{2}~~}{2}} \\\\\\ \sqrt{\cfrac{2+\sqrt{3}}{2}\cdot \cfrac{1}{2}}\implies \sqrt{\cfrac{2+\sqrt{3}}{4}}\implies \boxed{\cfrac{\sqrt{2+\sqrt{3}}}{2}} \\\\[-0.35em] ~\dotfill[/tex]
[tex]\cfrac{~~ sin\left( \frac{30^o}{2} \right)~~}{cos\left( \frac{30^o}{2} \right)}\implies \cfrac{~~\frac{\sqrt{2-\sqrt{3}}}{2} ~~}{\frac{\sqrt{2+\sqrt{3}}}{2}}\implies \cfrac{\sqrt{2-\sqrt{3}}}{2}\cdot \cfrac{2}{\sqrt{2+\sqrt{3}}} \\\\\\ \cfrac{\sqrt{2-\sqrt{3}}}{\sqrt{2+\sqrt{3}}}\implies \blacktriangleright \sqrt{\cfrac{2-\sqrt{3}}{2+\sqrt{3}}} \blacktriangleleft[/tex]
