If a circle has the area A and radius r, then
A = pi * r^2
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To calculate this you will need the diameter of the circle. The formula is: diameter/2*pi If you don't know the diameter you can also use the area of the circle: Sqrt(Area/pi) = radius
50.2656 square inches The formula to find the area of a circle is ∏r2. Where ∏ is the mathematical constant and r is the radius of the circle. So 3.14 x 42. = 50.27 square cm or yds, (whatever the diameter was in).
Area of a circle = pi*radius2
In order to convert the area of a circle to the circumference of the circle, divide by the radius and multiply by two. The formula for the circumference of a circle is pi times the diameter.
semi means half A semi-circle is half a circle The formula for the area of a circle is A = (Π * r^2) Area of semi circle = (Π * r^2) ÷ 2