Question: The length of the chord AB = 12 in. Find the radius of the circle O.

A ) 6
B ) 6 in.
C ) 7 in.
D ) 7
Steps to derive
1 Length of chord AB = 12 in..
2 AOB is a right triangle.
[Apply Pythagorean theorem.]
3 AB2 = OA2 + OB2
[Since, the radius of the circle = OA = OB.]
4 AB2 = 2OA2
5 OA2 =
[Divide by 2 on both sides.]
6 OA2 =
[Substitute AB.]
[Apply exponents and simplify.]
7 OA2 =
8 OA =
[Find the positive square root.]
9 The radius of the circle, O is 6
Hence the right answer is Option A
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