This page contains a collection of some of the best free Geometry teacher lesson plans from around the web. Great for use by teachers or home-school parents!

## Quadrilaterals in the Coordinate Plane

*Geometry Lesson Plan*

In this lesson, "Students will be able to apply definitions and theorems to verify special quadrilaterals using coordinate geometry." This lesson plan consists of a warm-up activity on slope then a main lesson where students must apply the slope formula, midpoint formula, and the distance formula to justify that a quadrilateral is a parallelogram given the coordinates of its vertices. This lesson plan contains two worksheets and a formula sheet handout.

## Pieces of Proof

*Geometry Lesson Plan*

"There is a leap to be made from understanding postulates and theorems in geometry to writing proofs using them. This lesson offers an intermediate step, in which students put together the statements and reasons to build a formal proof." This great lesson plan includes a handout containing six sample proofs.

## Transformations - Reflections & Dilations

*Geometry Lesson Plan*

"Students will be able to identify and compare the three congruence transformations, apply the three congruence transformations to coordinates of the vertices of figures, identify and apply dilations, and apply transformations to real-world situations." This lesson plan includes three worksheets: Reflections over Two Lines, Dilations using Measurement, and Transformations.

## Squares, Diagonals, and Square Roots

*Geometry Lesson Plan*

This lesson plan is on the "relationship between the lengths of the sides and diagonals of a square. Students will use their discoveries to predict the diagonal length of any square". This lesson plan contains worksheets, questions for students, assessment options, and extensions.

## Triangle Angle Sum Theorem

*Geometry Lesson Plan*

This lesson plan is on the Triangle Angle Sum Theorem. Objectives include: "Review some properties of angles and lines, explore some properties of triangles, and prove the Triangle Sum Theorem". This lesson plan requires GSP for lab activity.

## Fun with Angles (Formed by Parallel Lines)

*Geometry Lesson Plan*

This lesson plan will help the students visualize the different angles (corresponding, alternate interior, and same-side interior) when coplanar lines are cut by a transversal.

## Triangle Congruency Theorems & Fettuccine

*Geometry Lesson Plan*

In this lesson, "the students will use fettuccine noodles to discover the truth of different conjectures about triangle congruencies. They will develop an understanding of the triangle congruency theorems that will be used throughout geometry. A problem involving needing to find congruent triangles will be posed and students will begin with the most basic case and work toward the actual congruency theorems in solving this problem."

## Inequalities in Triangles

*Geometry Lesson Plan*

This is an outstanding lesson plan on Inequalities in Triangles. From the lesson, "Students will use pasta to create models of triangles and non-triangles and investigate the relationship between the longest side of the triangle and the sum of the other two sides of the triangle. In addition, students will measure the sides and angles of a scalene triangle and investigate the relationship between the location of the largest angle and largest side in a triangle." This complete lesson includes two activity worksheets (The Triangle Inequality and Inequalities for Sides and Angles), examples, assessment, and extensions.

## Trigonometry Puzzles

*Geometry Lesson Plan*

"This lesson offers a pair of puzzles to enforce the skills of identifying equivalent trigonometric expressons. Addtional worksheets enhance students' abilities to appreciate and use trigonometry as a tool in problem solving". In the first puzzle, students apply trig values for some common angles. In the second, students use trig identies to match equivalent expressions.

## Polygon Capture Game

*Geometry Lesson Plan*

This is a great lesson plan for teaching students to describe, classify, and understand relationships among types of polygons. From the lesson, "students classify polygons according to more than one property at a time. In the context of a game, students move from a simple description of shapes to an analysis of how properties are related". This lesson plan includes all necessary handouts and worksheets and includes extensions.

## Polygons - Sorting by Attributes

*Geometry Lesson Plan*

"Students identify and classify polygons according to various attributes. They then sort the polygons in Venn Diagrams, according to these attributes. Extensions to fundamental ideas about probability and statistics are also included." .

## Polygons - Sum of Interior and Exterior Angles

*Geometry Lesson Plan*

In this lesson, students will learn to find the sum of the interior and exterior angles of any polygon and to construct a polygon and its exterior angles given the number of sides.

## Angles, Polygons, Pythagorean Theorem, Basic Trig

*Geometry Lesson Plan*

This page contains five separate lesson plans:

- Lesson Plan 1: To identify and apply common properties of triangles, special quadrilaterals, and n-gons.
- Lesson Plan 2: To define and illustrate terms related to polygons, to classify quadrilaterals and polygons, to construct types of parallelograms, and to state and apply properties of parallelograms.
- Lesson Plan 3: To determine the sum of the measures of the interior and exterior angles of a convex polygon of n sides and to determine the measure of a central angle of a polygon.
- Lesson Plan 4: To calculate the length of a missing side of a right triangle using the Pythagorean Theorem, to use the converse of the Pythagorean Theorem, and to solve word problems.
- Lesson Plan 5: To calculate the measure of an angle or the length of a side of a right triangle using the tangent, sine, and cosine ratios.

## Liquid Volume

*Geometry Lesson Plan*

In this lesson, students will use the formulas for volume of rectangular prisms and cylinders and see the relationship between cubic centimeters and milliliters.

## Circle Packing

*Geometry Lesson Plan*

"In this unit, students explore circles. In the first lesson students apply the concepts of area and circumference to explore arrangements for soda cans that lead to a more efficient package. They then experiment with three-dimensional arrangements to discover the effect of gravity on the arrangement of soda cans in the second lesson. The final lesson allows students to examine the more advanced mathematical concept of curvature."

## Spherical Geometry - A Global Perspective

*Geometry Lesson Plan*

This lesson plan provides a very good introduction to spherical geometry. Students will "relate prior knowledge about the globe to definitions and properties in spherical geometry and given a common definition or property in Euclidean geometry, make a conjecture about the corresponding statement in spherical geometry."