What is a circle
Wiki: A circle is a closed curve where every point on the curve is a fixed distance from a point known as the centre. The distance between any of the points and the centre is called the radius. A circle is a shape of Euclidean geometry and divides the plane into two regions, an interior and an exterior.
In any circle, if you divide the circumference (distance around the circle) by its diameter (distance across the circle), you always get the same number Pi (π) which is approximately 3.142.
Properties
- Arc: Any connected part of the circle.
- Centre: the point equidistant from the points on the circle.
- Chord: a line segment whose end points lie on the circle
- Circular sector: A region bounded by two radii and an arc lying between the radii.
- Circular segment: a region in the circle not containing the centre, bounded by a chord and an arc lying between the chord’s endpoints.
- Circumference: the length of one circuit along the circle.
- Diameter: a line segment whose endpoints lie on the circle and which passes through the centre or the length of such a line segment, between any two points on the circle, it is a special case of a chord, namely the longest chord, and it is twice the radius.
- Passant: a coplanar straight line that does not touch the circle.
- Radius: a line segment joining the centre of the circle to any point on the circle itself; or the length of such a segment, which is half a diameter.
- Secant: an extended cord, a coplanar straight line cutting the circle of two points.
- Semicircle: a region bounded by a diameter and an arc lying between the diameter’s endpoints. It is a special case of a circular segment, namely the largest one.
- Tangent: a coplanar straight line that touches the circle at a single point.
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