Difference between revisions of "Two Tangent Theorem"

(add Power of Point)
(added proofs)
Line 1: Line 1:
 
The two tangent theorem states that given a circle, if P is any point lying outside the circle, and if A and B are points such that PA and PB are tangent to the circle, then PA = PB.
 
The two tangent theorem states that given a circle, if P is any point lying outside the circle, and if A and B are points such that PA and PB are tangent to the circle, then PA = PB.
 +
<geogebra>4f007f927909b27106388aa6339add09df6868c6</geogebra>
  
It follows from [[Power of a Point]] trivially, or we can use similar triangles, given that tangents to a circle form a right angle to the radius to the point of tangency.
+
== Proofs ==
 +
=== Proof 1 ===
 +
Since <math>OBP</math> and <math>OAP</math> are both right triangles with two equal sides, the third sides are both equal.
 +
 
 +
=== Proof 2 ===
 +
From a simple application of [[Power of a Point]], the result follows.
  
 
{{stub}}
 
{{stub}}
 
 
[[Category:Geometry]]
 
[[Category:Geometry]]

Revision as of 17:42, 10 March 2009

The two tangent theorem states that given a circle, if P is any point lying outside the circle, and if A and B are points such that PA and PB are tangent to the circle, then PA = PB.

<geogebra>4f007f927909b27106388aa6339add09df6868c6</geogebra> 

Proofs

Proof 1

Since $OBP$ and $OAP$ are both right triangles with two equal sides, the third sides are both equal.

Proof 2

From a simple application of Power of a Point, the result follows.

This article is a stub. Help us out by expanding it.