An isosceles triangle of sides 13cm, 13cm, 10cm is inscribed in a circle. What is the radius of the circle?

A.
7cm 
B.
12cm 
C.
8cm 
D.
7cm 
E.
69cm
Correct Answer: Option A
Explanation
In (Delta DAC, stackrelfrown{DAC} = theta)
(sin theta = frac{5}{13})
(theta = 22.6°)
(< DOC = 22.6° times 2 = 45.2°)
(sin 45.2 = frac{5}{r} implies r = frac{5}{sin 45.2})
(r = 7.046cm)
= (7frac{1}{24} cm)