A circle is a geometric figure plane figure formed by all the points that are at a distance less than or equal to a fixed value (called radius) with respect to a central point (called center). That is, includes both the circumference and the interior bounded by it.
A circumferenceinstead, it is a closed curved line and plane formed by all the points that are at an exact distance (the radius) from the center. It has no area, only length.
The difference between the two is that the circle includes the inner area, while the circumference is only the outline or edge of the circle.
| Circle | Circle | |
|---|---|---|
| Definition | A flat surface bounded by a circumference. | Curved line bounding and containing a circle. |
| Parts |
|
|
| Length measurement | Area | Perimeter |
| Formula |
A= π. r2 |
P= 2r.π |
What is a circle
A surface composed of a series of outer points, called a circumference, and all the points inside it.
Being a flat surface, every circle has an area.
The formula for calculating the area is:
A= π. r2
The area of a circle is equal to Pi (3.1416) multiplied by the radius squared.
Parts of a circle
- Arcis a portion of the circle formed by a curve joining two points.
- Stringis the distance between two points of an arc.
- Radiusis the distance from the center of the circle to any of the points on the circle. It is half the distance of the diameter.
- Diameteris the distance between two points passing through the center of the circle. That is, twice the distance of the radius.
- Centeris the point where all other equidistant points of the circle converge.
What is a circle
A circumference is a continuous, flat, closed, curved line composed of a series of points that are equidistant from a common center.
Since the circumference is a line and is not a flat surface, it has no area, but it does have perimeter.
The formula to calculate the perimeter is:
P= 2r.π
The perimeter is equal to the radius multiplied by 2 and this product in turn is multiplied by Pi (3.1416).
Parts of a circle
A circumference shares the elements of a circle (arc, chord, radius, diameter and center), but in addition it has:
- Tangent line: is a straight line that touches the circle at a single point.
- Secant line: is a straight line that cuts the circle at two points.
See also Types of angles and Equilateral, isosceles and scalene triangle.
