Theorem of Equal Chords Subtending Angles at the Center
In the given ...
Question
In the given figure, O is the centre of a circle in which chords AB and CD intersect at P such that PO bisects ∠BPD. Prove that AB = CD.
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Solution
Given: O is the centre of a circle in which chords AB and CD intersect at P such that PO bisects ∠ BPD. To prove: AB = CD Construction: Draw OE ⊥ AB and OF ⊥ CD Proof: In Δ OEP and Δ OFP, we have: ∠ OEP = ∠ OFP (90° each) OP = OP (Common) ∠ OPE = ∠ OPF (∵ OP bisects ∠BPD ) Thus, Δ OEP ≅ Δ OFP (AAS criterion) ⇒ OE = OF Thus, chords AB and CD are equidistant from the centre O. ⇒ AB = CD (∵ Chords equidistant from the centre are equal) ∴ AB = CD