In the figure, O is the centre of the circle, BO is the bisector of ∠ABC. Show that AB = BC.
Given: In the figure, a circle with centre O, OB is the bisector of ∠ABC
To prove : AB = BC
Construction : Draw OL ⊥ AB and OM ⊥ BC
Proof : In ΔOLB and ΔOMB,
∠1=∠2 (Given)
∠L=∠M (Each=90∘)
OB=OB (Common)
∴ΔOLB≅ΔOMB (AAS criterion)
∴OL=OM (c.p.c.t)
But these are distance from the center and chords equidistant from the centre are equal
∴ Chord BA=BC
Hence, AB=BC