if you are given a diameter divide it by two to get the radius! From then on, it is just simple
Pi R Squared
Circumference = (diameter) multiplied by (pi)
The area of a circle can be found with the formula (pi)r^2
You neglected to say whether the 4mm is the radius of the circle, or the diameter,or the circumference. Each possibility leads to a different area.
To find the circumference of a circle then multiply pi (3.14159265...) by the diameter of the circle. To find the area then multiply pi by the radius squared.
Area = pi*d2/4 = pi*r2 where d is the diameter, and r is the radius = diameter/2
Area = Pi(d/2)2 where d = diameter
Area of Circle = pi (radius)2 So , using this formula we can find the radius and also the diameter. Diameter = 2(radius)
In order to find the diameter of a circle if you have the area is to rearrange the formula for the area of a circle to put diameter as the unknown, like so: PIE*d = Area of a Circle d = (Area of a Circle) / PIE Therefore if the area of your circle is 40cm, 40/PIE = 12.73cm and that's the diameter.
I assume that you are referring to the area of a circle. You divide the diameter in half to find the radius and then you put it into the formula.
Divide the circumference by pi, and that will give you the diameter. Then take half of the diameter (the radius), and plug it into the formula for the area of a circle (A=πr²)
(Pi)r^2=area & 2r=d
If: pi*radius2 = area Then: radius = square root of (area/pi) And: diameter = 2*radius
To find the area of a circle, either the diameter or the circumference must be known. The formula for the area from the diameter is (pi)*(1/2 of diameter) squared. From the circumference, simply substitute (circumference / pi) for diameter.
First find out the radius (it is simply half the diameter). Then use the formula area = pi x radius2.
When the diameter is 2.9 the radius is 1.45. To find the area of a circle you need to use this formula r2*pi In this case it will be 1.45*1.45*3.14=6.6
To find the area of a circle, here is the formula: A=Pi r2 To find area, you must square the radius and multiply it by pi. If it gives you the diameter, not the radius, divide the diameter by 2, that gives you the radius, then square it and multiply by pi.
If you have the circumference: circumference = (pi) * diameter diameter = circumference / (pi) If you have the area: area = (pi) * radius * radius radius = square_root(area / pi) radius = diameter / 2 diameter = 2 * square_root(area / pi)