Lesson Plan: Parallel Chords and Tangents in a Circle Mathematics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to use the parallel chords and the parallel tangents and chords of a circle to deduce the equal measures of the arcs between them and find missing lengths or angles.

Objectives

Students will be able to

• understand that the measures of the arcs between parallel chords of a circle are equal,
• understand that the measures of the arcs between a chord and a parallel tangent of a circle are equal,
• understand that if the measures of the arcs between two chords (or between a chord and a tangent) are equal, we can deduce that the lines must be parallel,
• use theories of parallel chords and parallel chords and tangents to find unknown angles and lengths.

Prerequisites

Students should already be familiar with

• chords and tangents of a circle,
• the Pythagorean theorem,
• the central angle theorem and arc measures,
• the relationship between equal arcs and chords.

Exclusions

Students will not cover

• the equation of a line (in any form),
• the equation of a circle.