If ABC is an equilateral triangle inscribed in a circle and P be any point on the minor arc BC which does not coincide with B or C, prove that PA is the angle bisector of BPC.
Let DABC be an equilateral triangle inscribed in a circle with centre O.
So all sides of this equilateral triangle are equal by definition
AB = AC = BC
Now we know that equal chords subtend and equal angles at the centre. So,
AOB = AOC =BOC … (i)
Consider the arc AB, AOB and APB are the angles subtended by AB at the centre and at the remaining part of the circle
Therefore
… (ii)
Similarly,
… (iii)
Using (i), (ii) and (iii), we have
APB = APC
Hence, PA is the angle bisector of BPC.
Hence proved