Construction: Draw lines OB, OC, and OD.
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In ΞAOB,
OA = OB (Radii of the same circle)
Thus, β OAB = β OBA = 40Β°.
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(Angles opposite to equal sides of a triangle).
So, by angle sum property, β AOB = 100Β°.
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Since the chords AB and CD are equal in length, the angles subtended by them at the centre will be equal.
Hence, β AOB = β COD = 100Β°.
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