Question

A square is inscribed in a circle with an area of 10 pi square inches. what is the area of the square

Answer 1

We need to determine the radius and diameter of the circle.  If the area of the circle is 10 pi in^2, then, according to the formula for the area of a circle,

A = 10 pi in^2 = pi*r^2.  Thus, 10 in^2 = r^2, and r = radius of circle = sqrt(10) in.

Thus, the diam. of the circle is 2sqrt(10) in.  This diam. has the same length as does the hypotenuse of one of the triangles making up the square.

Thus, [ 2*sqrt(10) ]^2 = x^2 + x^2, where x represents the length of one side of the square.  So, 4(10) in^2 = 2x^2.  Then:
                                 40 in^2  = 2x^2, or 20 in^2 = x^2, and so the length x of one side of the square is sqrt(20).  The area of the square is the square of this result:

Area of the square = x^2 = [ sqrt(20) ]^2 = 20 in^2 (answer).  Compare that to the 10 pi sq in area of the circle (31.42 in^2).