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Circle

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Sector Calculator

rotating circle

circle approximations

Area:
circumference:
diameter:

radius:

Enter any one known value

area:
c:
d:
r:
circle image

Only Two Values Required


Circle Tutorial

Circle formulas are shown below:

\text{radius}=\frac{\text{diameter}}{\text{2}}

\text{diameter}=\text{radius}\cdot 2

\text{circumference}=\text{diameter}\cdot \pi

\text{area}=\pi \cdot \text{radius}^2



The circumfrence of a circle is the perimiter of the circle or the distance around the circle. The diameter of a circle is the distance from opposite points on the circle and also the height of a circle. The radius of a circle is the distance from the center of a circle to any point on a circle and is half the length of the diameter. The area of a circle is the total amount surface of a circle. Finding values in a circle is very simple because only one value in a circle is needed to find all other values. If given the radius then the diameter is already two times that value and if given the diameter, the radius is half of that value. If told to find all values of a cricle given a radius of length 7, you can use the calculation process shown below:

Finding the diameter

\text{diameter}=\text{radius}\cdot 2

\text{diameter}=(7)\cdot \text{2}

\text{diameter}=14



Finding the circumference

\text{circumference}=\text{diameter}\cdot \pi


\text{circumference}=(14)\cdot \pi


\text{circumference}=14\pi




Finding the area

\text{area}=\pi \cdot \text{radius}^2


\text{area}=\pi \cdot (7)^2


\text{area}=49\pi


As you can see the circumference is 14 pi, the diameter is 14, and the area is 49 pi. When solving circles you are not limited to needing the radius first. For example all values of a circle with a circumfrence of 58 pi can be calculated. The first and only value that can possibly be calculated is the diameter. Since the circumfrence is equal the the diameter times pi, the diameter miust be equal to the circumfrence divided by pi. This means the diamer is 58. Now that the diameter is known, the radius can be found. Since the radius is half of the diameter it must be 58 divided by 2 which equals 29. The final value to be calculated is the area of the circle. The formula for the area is pi times the radius squared. According to this formula the area of the circle must equal approximately 2642 after subsituting known values into the formula.