Recalling the formula for the area of a circle:
[tex]A=\pi\cdot r^2[/tex]Divide both sides of the equation by the constant pi :
[tex]\frac{A}{\pi}=r^2[/tex]Take the square root of both sides of the equation and take the positive value of the square root, since r is a length and it is positive:
[tex]\sqrt[]{\frac{A}{\pi}}=\sqrt[]{r^2}=r[/tex]Therefore:
[tex]r=\sqrt[]{\frac{A}{\pi}}[/tex]Since A=25, then:
[tex]r=\sqrt[]{\frac{25}{\pi}}=\frac{\sqrt[]{25}}{\sqrt[]{\pi}}=\frac{5}{\sqrt[]{\pi}}[/tex]Use a calculator to find out the decimal representation of the number 5/sqrt(pi):
[tex]r=\frac{5}{\sqrt[]{\pi}}\approx2.821[/tex]Therefore, the radius of a circle with area 25 is approximately 2.821.
