In figure, AB and CD are equal chords of a circle whose centre is O. If OM ⊥ AB and ON ⊥ CD, prove that ∠OMN = ∠ONM.
AB and CD are equal chords of a circle whose centre is O. When produced, these chords meet at E. Prove that EB = ED and AE = CE.
Given: Bisector AD of ∠BAC of ∆ABC passes through the centre O of the circumcircle of ∆ABC.
To Prove: AB = AC.
Construction: Draw OP ⊥ AB and OQ ⊥ AC.
Proof:
In ∆APO and ∆AQO,
∠OPA = ∠OQA
| Each = 90° (By construction)
∠OAP = ∠OAQ | Given
OA = OA | Common
∴ ∆APO ≅ ∆AQO | AAS
∴ OP = OQ | C.P.C.T.
∴ AB = AC.
| ∵ Chords equidistant from the centre are equal.