Power of a point theorem
Contents
Theorem:
There are three unique cases for this theorem. Each case expresses the relationship between the length of line segments that pass through a common point and touch a circle in at least one point.
Case 1 (Inside the Circle):
If two chords and
intersect at a point
within a circle, then
draw(circle((0,0),3)); dot((0,0)); dot((-2.82, 1)); label("A"(-2.82,1)); (Error making remote request. Unknown error_msg)
Case 2 (Outside the Circle):
Classic Configuration
Given lines and
originate from two unique points on the circumference of a circle (
and
), intersect each other at point
, outside the circle, and re-intersect the circle at points
and
respectively, then
Tangent Line
Given Lines and
with
tangent to the related circle at
,
lies outside the circle, and Line
intersects the circle between
and
at
,
Case 3 (On the Border/Useless Case):
If two chords, and
, have A on the border of the circle, then the same property such that if two lines that intersect and touch a circle, then the product of each of the lines segments is the same. However since the intersection points lies on the border of the circle, one segment of each line is
so no matter what, the constant product is
.