Question

In figure 2, O is the center of the circle and B is a point on the circle. In rectangle OABC, if OA-5 and OC -6, what is the area of the circle?
A) 11 pie
B) 25 pie
C) 36 pie
D) 61 pie

Answer 1

The formula of an area of a circle:

$A_O=\pi r^2$

Use the Pythagorean theorem to calculate a length of a radius.

$r^2=5^2+6^2\\\\r^2=25+36\\\\r^2=61\to r=\sqrt{61}$

The area of a circle:

$A_O=\pi\cdot(\sqrt{61})^2=61\pi$

Answer: D) 61π