# How to find the diameter of a circle?

The diameter of a circle is called a line segment that connects the two points of the circle most distant from each other, passing through the center of the circle. The name diameter came from Greek and literally means cross. The diameter is denoted by the Latin alphabet letter D or by the symbol O.

## Diameter of circle

In order to know how to find the diameter of a circle, you need to refer to the formulas. The basic formulas by which you can calculate the diameter of a circle are two. The first is D = 2R. Here the diameter is equal to twice the radius, where the radius is the interval from the center to any of the points of the circle (R). Consider an example, if a radius is known in a task and it is 10 cm, then you can easily find the diameter. For this radius value we substitute into the formula D = 2 * 10 = 20 cm

The second formula makes it possible to find the diameter along the circumference and it looks like D = L / P, where L is the value of the circumference and P is the number of pi, which is approximately equal to 3.14.This formula is very convenient to apply in practice. If you need to know the diameter of the hatch, the cover on the tank, of a pit, you just have to measure their circumference and divide it by 3.14. For example, the circumference is 600 cm, hence D = 600 / 3.14 = 191.08 cm.

## Diameter of circumcircle

The diameter of the circumcircle can also be found if it is described or inscribed in a triangle. To do this, you first need to find the radius for the inscribed circle using the formula: R = S / p, where S denotes the area of the triangle, and p is its semi-perimeter, p equates to (a + b + c) / 2. After the radius is known, you need to use the first formula. Or immediately substitute all values in the formula D = 2S / p.

If you do not know how to find the diameter of the circle described, use the formula to find the radius of the circle described around the triangle. R = (a * b * c) / 4 * S, S in the formula indicates the size of the area of a triangle.