# Geometry/Chapter 9/Lesson 2

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## Introduction[edit | edit source]

- Properties of Tangents
- Properties of Arcs and Chords

## Properties of Tangents[edit | edit source]

**If a line is a tangent to a circle, then it is perpendicular to the radius drawn to the point of tangency.**

With this property, your teachers will usually throw **Pythagorean triples** at you for you to solve. Yes... these triples still matter. For example:

AB is tangent to C at [point] D. Find the length of a radius of C.
Remember: Tangent AB and a radius of C form a right triangle. Use the Pythagorean theorem with whatever inputs your teacher decides to use. |

**If a line in the same plane as a circle is perpendicular to a radius at its endpoint on the circle, then the line is a tangent to the circle.****Two segments tangent to a circle form a point outside the circle are congruent.**