# Geometric Proof Teacher Resources

Find Geometric Proof lesson plans and worksheets
Showing 118 resources
Lesson Plan
EngageNY

#### Triangle Congruency Proofs (part 2)

For Teachers 9th - 10th Standards
Looking to challenge your students that have mastered basic triangle congruence proofs? A collection of proofs employ previously learned definitions, theorems, and properties. Pupils draw on their past experiences with proofs to...
Lesson Plan
EngageNY

#### Informal Proofs of Properties of Dilations

For Teachers 8th Standards
Challenge the class to prove that the dilation properties always hold. The lesson develops an informal proof of the properties of dilations through a discussion. Two of the proofs are verified with each class member performing the...
Lesson Plan
EngageNY

#### Informal Proof of the Pythagorean Theorem

For Students 8th Standards
Prove the Pythagorean Theorem using multiple informal proofs. Scholars first develop an understanding of the origins of the Pythagorean Theorem through proofs. They round out the lesson by using the theorem to find missing side lengths...
Instructional Video9:36
2
2
Flipped Math

#### Proving Lines Parallel

For Students 9th - 12th Standards
Show it can all be proved. Scholars learn the converses of the properties of parallel lines. Using the converses, pupils determine which lines are parallel based on angle measurements and practice using a flow proof to show that two...
Instructional Video5:17
TED-Ed

#### How Many Ways Are There to Prove the Pythagorean Theorem?

For Students 8th - 12th Standards
There is more than one way to prove the Pythagorean Theorem. Euclid and Einstein found the same way to prove the Pythagorean Theorem. The video introduces several other ways to prove the theorem along with the history of its use.
Instructional Video3:11
CK-12 Foundation

#### Two-Column Proofs: Lesson

For Students 9th - 12th
Why is it a two-column proof? A video introduces the class to the concept of a two-column proof and how to set one up. The segment of a playlist on basic geometry highlights the types of reasons that can be in a proof.
Instructional Video7:37
Brightstorm

#### Pythagorean Theorem Proofs

For Students 10th - 12th Standards
Your class knows the Pythagorean Theorem, but can they prove it? A series of three videos shows two proofs of the Pythagorean Theorem and use it to classify triangles.
Lesson Plan
Virginia Department of Education

#### Congruent Triangles

For Teachers 9th - 11th Standards
Is this enough to show the two triangles are congruent? Small groups work through different combinations of constructing triangles from congruent parts to determine which combinations create only congruent triangles. Participants use the...
Unit Plan
Mathematics Vision Project

#### Connecting Algebra and Geometry

For Teachers 9th - 10th Standards
Connect algebra and geometry on the coordinate plane. The eighth unit in a nine-part integrated course has pupils develop the distance formula from the Pythagorean Theorem. Scholars prove geometric theorems using coordinates including...
Lesson Plan
EngageNY

#### Comparing the Ratio Method with the Parallel Method

For Students 9th - 10th Standards
Can you prove it? Lead your class through the development of the Side Splitter Theorem through proofs. Individuals connect the ratio and parallel method of dilation through an exploration of two proofs. After completing the proofs,...
Lesson Plan
EngageNY

#### Informal Proof of AA Criterion for Similarity

For Teachers 8th Standards
What does it take to show two triangles are similar? The 11th segment in a series of 16 introduces the AA Criterion for Similarity. A discussion provides an informal proof of the theorem. Exercises and problems require scholars to apply...
Lesson Plan
EngageNY

#### Converse of the Pythagorean Theorem

For Students 8th Standards
Discover a new application of the Pythagorean Theorem. Learners prove and apply the converse of the Pythagorean Theorem in the 17th instructional activity in a 25-part series. The examples ask learners to verify right triangles using the...
Instructional Video0:53
Corbett Maths

#### Angles in the Same Segment – Proof

For Students 8th - 12th Standards
If angles intercept the same arc, the angles must be the same size. The quick video talks through the proof of showing the reason two inscribed angles that intersect the same arc have the same measurement. Pupils then create their own...
Instructional Video22:15
2
2
Flipped Math

#### Intro to Proofs

For Students 9th - 12th Standards
Prove the best way to keep up in Geometry. Scholars first review algebraic properties from Algebra. Learners then use the properties to create two-column proofs to solve linear equations before completing algebraic proofs by providing...
Lesson Plan
EngageNY

#### Congruence Criteria for Triangles—ASA and SSS

For Students 9th - 10th Standards
How do you know if a pair of triangles are congruent? Use the lesson to help class members become comfortable identifying the congruence criteria. They begin with an exploration of ASA and SSS criteria through transformations and...
Instructional Video3:13
Corbett Maths

#### Alternate Segment Theorem – Proof

For Students 6th - 12th Standards
Scholars observe a video explaining the alternate segment theorem proof. Then, they apply the theorem to additional practice problems from the text and complete a worksheet.
Handout
Charleston School District

#### Pythagorean Theorem and Converse

For Students 8th Standards
You've heard that it is true, but can you prove it? Scholars learn the Pythagorean Theorem through proof. After an overview of proofs of the theorem, learners apply it to prove triangles are right and to problem solve. This is the second...
Instructional Video14:37
2
2
Flipped Math

#### Parallel Lines and Triangles

For Students 9th - 12th Standards
Triangles bring sums to geometry. The lesson presents two theorems dealing with the angles of a triangle. Pupils learn about the Triangle Sum Theorem and the Exterior Angle Theorem, and then apply the theorems to create equations and...
Worksheet
Mt. San Antonio Collage

#### Elementary Geometry

For Students 9th - 12th Standards
Your class may believe that geometry is a trial, but they don't know how right they are. A thorough math lesson combines the laws of logic with the laws of geometry. As high schoolers review the work of historical mathematicians and the...
Lesson Plan
2
2
Illustrative Mathematics

#### Are They Similar?

For Teachers 9th - 11th Standards
Learners separate things that just appear similar from those that are actually similar. A diagram of triangles is given, and then a variety of geometric characteristics changed and the similarity of the triangles analyzed. Because the...
Handout
Mt. San Antonio Collage

#### Congruent Triangles Applications

For Students 9th - 12th Standards
Triangles are all about threes, and practicing proving postulates is a great way to get started. The first page of the worksheet provides a brief introduction of the different properties and postulates. The remaining pages contain...
Assessment
Inside Mathematics

#### Rhombuses

For Teachers 9th - 12th Standards
Just what does it take to show two rhombuses are similar? The assessment task asks pupils to develop an argument to show that given quadrilaterals are rhombuses. Class members also use their knowledge of similar triangles to show two...
Instructional Video16:20
2
2
Flipped Math

#### Prove Triangles Similar

For Students 9th - 12th Standards
Show more than one way to prove similarity. Scholars learn three different methods to show two triangles are similar, Angle-Angle, Side-Side-Side, and Side-Angle-Side. Pupils practice applying these methods to determine whether two given...
Lesson Plan
EngageNY

#### Special Lines in Triangles (part 2)

For Teachers 9th - 10th Standards
Medians, midsegments, altitudes, oh my! Pupils study the properties of the median of a triangle, initially examining a proof utilizing midsegments to determine the length ratio of a median. They then use the information to find missing...