Use PI to find the radius in a known area of a circle. This constant specifies the ratio between the diameter of the circle and the length of its border (circumference). The circumference determines the maximum area plane, which is possible to cover, and the diameter equals two radii, and therefore the area with the radius is also related to each other with a ratio that can be expressed through the number PI. This constant (π) is defined as the ratio of the area (S) and the squared radius (r) of the circle. This implies that the radius can be expressed as the square root of the private from dividing the area by PI: r=√(S/π).
Use any calculator for practical calculations to find the circle's radius at the famous square, how to find square roots in the mind is somewhat difficult for a person not having outstanding abilities in mathematics. Do not have to use the calculator as a standalone device - it could be a software calculator for Windows which you can run by pressing hotkeys Win + R, then typing calc and pressing Enter. If this calculator is switched to "engineering" or "scientific" mode, selecting the appropriate item under "View" menu, you will not have to manually enter the value of PI for this interface is added to a separate button. The operation of taking the square root in this embodiment, the calculator interface is implemented using the button x^2 when you set the mark in the checkbox Inv, and the division operation required in the computation of the radius, nothing special here.
Use the calculator built into some of the search engines if you don't want to deal with push-button interface. For example, to calculate the radius of the circle whose area is fifty meters, go to google.com and enter a search term sqrt(50/pi). Google will calculate and show the result 3,9894228.