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Question
Out of the two concentric circles, the radius of the outer circle is 5 cm and the chord AC of length 8 cm is a tangent to the inner circle. Find the radius of the inner circle.
Solution
From the figure,
Chord AB = 8 cm
OC is perpendicular to the chord AB
AC = CB = 4 cm
In right triangle OCA
OC2 + CA2 = OA2
OC2 = 52 – 42
= 25 – 16
= 9
OC = 3 cm
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