As a result, the perimeter of the semicircle is also half.Īrea of the semi-circle is the region occupied by a semi-circle. Semicircular shapes are formed when two equal parts are divided by a circle.

The radius of a circle formula from circumference is: Radius = Circumference/2π or C/2π units.

The radius of a circle formula from diameter is: Radius = Diameter/2 or D/2 units.

If your length for both sides ranged at 4 units out from the midpoint, your final number would be 16 units in total or 2-5/16ths (in case of fractions). The radius is calculated by taking one-half of the diameter, and then calculating how far it is out from that point to each side of the radius.įor example, if your diameter were 10 units, you would calculate your radius as 5 units on each side. The radius of a circle is the distance from the centre point on its circumference to its edge.

In either case, you need a radius as input and an output value for the radius squared equal to the circle's area. There are two possible formulas, one using circumferences and the other using radii. Ĭircumference is often misspelled as circunference.The pattern to find the area is to multiply by pi. If you input the radius in centimeters, you will get the answer in square centimeters (cm²), if in inches, will get the answer in square inches (in²) and so on. For simplicity, you can use Pi = 3.14 or Pi = 3.1415. Π represents the number Pi which is defined as the ratio of the circumference of a circle to its diameter or π = C d.

The diameter is twice the radius or d = 2 The diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. The radius is half the diameter or r = d 2. The radius of a circle is any of the line segments from its center to its perimeter. See below some definitions related to the formulas: CircumferenceĬircumference is the linear distance around the circle edge.

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21 inch radius what is the area