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: In figure, AB and AC are two equal chords of a circle whose centre is O. OD ⊥ AB and OE ⊥ AC.
To Prove: ADE is an isosceles triangle.
Proof: ∵ AB = AC
∴ OD = OE
| ∵ Equal chords are equidistant from the centre
∴ In ∆ODE,
∠ODE = ∠OED
| Angle opposite to equal sides
⇒ 90° - ∠ODE = 90° - ∠OED
⇒ ∠ODA - ∠ODE = ∠OEA - ∠OED
⇒ ∠ADE = ∠AED
∴ AD = AE
| Sides opposite to equal angles
∴ ∆ADE is an isosceles triangle.