therefore this forms an isosceles triangle inside the circle. Also, note that since triangle AOB is isosceles, then \(\angle OAB=\angle OBA\). \(\angle AOC\) is a straight angle, so will add up to ...

In order to derive the formula to calculate the angle at the centre of the sector, the formulae for the arc length and area of a sector can be rearranged so that we can calculate the fraction of ...