[tex]\tan 60^{\circ}~\text{equals y coordinate divided by x coordinate, where }(x,y) = \left(\dfrac 12, \dfrac{\sqrt 3}2 \right)[/tex]
[tex]\tan 60^{\circ}\\\\= \dfrac yx \\\\\\=\dfrac{\sin 60^\circ}{\cos 60^\circ}\\\\\\=\dfrac{\tfrac{\sqrt 3}2}{\tfrac 12}\\\\\\=\dfrac{\sqrt 3}2 \times 2\\\\\\=\sqrt 3[/tex]
This rule is enough
Now
Here A=60°