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Heron's Formula

Question
CBSEENMA9002969

Recall that two circles are congruent if they have the same radii. Prove that equal chords of congruent circles subtend equal angles at their centres.

Solution

Given: AB and CD are two equal chords of congruent circles with centres O and O' respectively.
To Prove: ∠AOB = ∠CO'D.
Proof: In ∠OAB and ∠O'CD,
OA = O'C
| Radii of congruent circles
OB = O'D
| Radii of congruent circles

AB = CD    | Given
∴ ∆OAB ≅ ∆O'CD    | SSS Rule
∴ ∠AOB = ∠CO'D.    | C.P.C.T.