Algebra 2 Math problem?

A regular pentagon means that it is composed of 5 equilateral triangles. The circle is inscribed, meaning it is inside the pentagon. Since it is a regular pentagon, the circle would be tangent to (touching) the centers of each side of the pentagon. To find the radius, which is also just the median of one of the equilateral triangles, you would divide 42.8 by 2 and then multiply by square-root-of-3. Your answer is 21.4 times the square root of 3.