Area of a circle Area of a circle In geometry, the area enclosed by a circle of radius is . Here the Greek letter represents a constant, approximately equal to 3.14159, which is equal to the ratio of the circumference of any circle to its diameter. One method of deriving this formula, which originated with Archimedes, involves viewing the circle as the limit of a sequence of regular polygons. The area of a regular polygon is half its perimeter multiplied by the distance from its center to its sides, and the corresponding formula (that the area is half the perimeter times the radius, i.e.
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