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Question
Two circles of radii 5 cm and 3 cm are concentric. Calculate the length of a chord of the outer circle which touches the inner.
Solution
OS = 5 cm
OT = 3 cm
In Rt. Triangle OST
By Pythagoras Theorem,
ST2 = OS2 – OT2
ST2 = 25 – 9
ST2 = 16
ST = 4 cm
Since OT is perpendicular to SP and OT bisects chord SP
So, SP = 8 cm
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