Power of a point P intersects the circle at A and B, the endpoints of the diameter. Their respective products of distances are equal to each other and to the power of point P in that circle This equality is sometimes known as the ""secant-tangent theorem"", ""intersecting chords theorem"", or the ""power-of-a-point theorem"". The power of a point is used in many geometrical definitions and proofs. For example, the radical axis of two given circles is the straight line consisting of points that have equal power to both circles. For each point on this line, there is a unique circle centered on that point
Distance from a point to a line the same point and the line is |"ax" + "c"| / |"a"|, as measured along a horizontal line segment. If the line passes through two points "P"=("x","y") and "P"=("x","y") then the distance of (x,y) from the line is: The denominator of this expression is the distance between "P" and "P". The numerator is twice the area of the triangle with its vertices at the three points, (x,y), "P" and "P". See: . The expression is equivalent to formula_4, which can be obtained by rearranging the standard formula for the area of a triangle: formula_5, where "b" is the length of