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 has coordinates: Horizontal and vertical lines In the general equation of a line, "ax" + "by" + "c" = 0, "a" and "b" cannot both be zero unless "c" is also zero, in which case the equation does not define a line. If "a" = 0 and "b" 0, the line is horizontal and has equation "y" = -"c"/"b". The distance from ("x", "y") to this line is measured along a vertical line segment of length |"y" - (-"c"/"b")| = |"by" + "c"| / |"b"| in accordance with the formula. Similarly, for vertical lines ("b" = 0) the distance between