This article is semi-protected until October 12, 2019. This article is about the shape and mathematical concept. This article is about circles in Euclidean geometry, and, in particular, the Euclidean plane, except where otherwise noted. Circle of profit free pdf download circle is a plane figure bounded by one line, and such that all right lines drawn from a certain point within it to the bounding line, are equal.

The bounding line is called its circumference and the point, its centre. It is a special case of a chord, namely the longest chord, and it is twice the radius. The circle has been known since before the beginning of recorded history. Natural circles would have been observed, such as the Moon, Sun, and a short plant stalk blowing in the wind on sand, which forms a circle shape in the sand. Plato explains the perfect circle, and how it is different from any drawing, words, definition or explanation. The circle is the plane curve enclosing the maximum area for a given arc length.

For a circle centred at the origin, i. The circle is the shape with the largest area for a given length of perimeter. Through any three points, not all on the same line, there lies a unique circle. Chords are equidistant from the centre of a circle if and only if they are equal in length.