In the given figure, BOC is a diameter of a circle with centre O. If AB and CD are two chords such that AB || CD. If AB = 10 cm, then CD = ?

Given: AB||CD and AB = 10cm


Construction: Drop perpendiculars OE and OF on to AB and CD respectively.


Now,


Consider ΔBOE and ΔCOF


Here,


OB = OC (radius)


OEB = OFC (right angle)


COF = BOE (vertically opposite angles)


By AAS congruency ΔBOE ΔCOF


OE = OF (by congruent parts of congruent triangles)


Chords equidistant from center are equal in length


That is CD = AB = 10cm


CD = 10cm

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