Area of a circle Measurement of a Circle" (c. 260 BCE), compare the area enclosed by a circle to a right triangle whose base has the length of the circle's circumference and whose height equals the circle's radius. If the area of the circle is not equal to that of the triangle, then it must be either greater or less. We eliminate each of these by contradiction, leaving equality as the only possibility. We use regular polygons in the same way. Suppose that the area "C" enclosed by the circle is greater than the area "T" = ⁄"cr" of the triangle. Let "E" denote
Distance from a point to a line equation of a line can be given in vector form: Here is the position of a point on the line, and is a unit vector in the direction of the line. Then as scalar "t" varies, gives the locus of the line. The distance of an arbitrary point to this line is given by This formula can be derived as follows: formula_39 is a vector from to the point on the line. Then formula_40 is the projected length onto the line and so is a vector that is the projection of formula_39 onto the line. Thus is the component of