AB and AC are two equal chords of a circle. Prove that the bisector of the angle BAC passes through the centre of the circle.
Given: AB and AC are two equal chords of the circle.
Prove: The Centre lies on the bisector of the BAC.
Construction: Join BC
Proof: In AOB and
AOC
AB = AC (given)
BAO =
CAO (given)
AO = AO (common)
AOB
AOC (by SAS congruence)
BO = CO (CPCT) …(i)
and AOB =
AOC (CPCT)
AOB +
AOC = 180° (Linear pair)
2
AOB = 180° (
APB =
APC)
AOB = 90°
AO is the perpendicular bisector of the chord BC and BC is the diameter as BO = CO
Hence, AO passes through the centre of the circle, and O is the centre of the circle.
Hence proved