A circle can be defined in different ways but a circle is always a two-dimensional shape that is perfectly uniform. If one were able to consciously look out from the precise center of a circle, all the parts of the circle would look exactly the same. The only other shape like this is the spehere.
Using points, the circle can be thought of as the set of all points that are equidistant from a center point. On a graph, the circle can be defined as [x2 + y2 = 1] to be centered at the origin.
Using a line of length [r], we can draw a circle by rotating the line in from its origin in 3600.
The circumference of a circle (or the perimeter of a circle) is equivalent to 
multiplied by the diameter of a circle, which is twice its radius [ C = d ].
The area of a circle is multiplied by the circle's radius squared [ A = r 2 ].
The circle to the right is called "circle E", because circles are named for their center points.
An optical illusion takes place when the circle is drawn between the lines of a square and when a diamond is drawn inside the square in which the circle appears to be "squished".
This is because certain assumptions in our minds work on the image and attempt to make sense of it at a deep, computational level.
Our minds are essentially attempting to shift between a gestalt representation of the circle and of the linear edges at the same time, resulting in the optical illusions found when we concentrate on the image to the right in various ways.
The radius of circle E is given by line segment DE. The diameter of circle E is given by line segment DF.
A chord of circle E is given by DH. A chord is any line that passes through two points on the perimeter of a circle. |
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The tangent of a circle is any line that passes through only one point on the circle, such as line segment AG. Keep in mind this image is a crude representation made in an attempt to highlight the concept of points and how lines and circles are both composed of and pass through various points in space.
