Illustrative Mathematics
Similar Triangles
Proving triangles are similar is often an exercise in applying one of the many theorems young geometers memorize, like the AA similarity criteria. But proving that the criteria themselves are valid from basic principles is a great...
EngageNY
Congruence Criteria for Triangles—SAS
Looking for a different approach to triangle congruence criteria? Employ transformations to determine congruent triangles. Learners list the transformations required to map one triangle to the next. They learn to identify congruence if...
Curated OER
Similar Triangles - Applied Problems
Students differentiate between similar and congruent triangles. In this geometry lesson, students identify the angles of triangles using the similarity theorem. They apply concepts of triangles to the real world.
Curated OER
Similar Triangles
Ninth graders find the height of every day objects using techniques learned through postulates that allow triangles in a problem to be similar. They calculate the length of a missing side and solve proportions.
EngageNY
The Side-Angle-Side (SAS) and Side-Side-Side (SSS) Criteria for Two Triangles to Be Similar
Playing with mathematics can invoke curiosity and excitement. As pupils construct triangles with given criteria, they determine the necessary requirements to support similarity. After determining the criteria, they practice verifying...
Curated OER
When Does SSA Work to Determine Triangle Congruence?
Your learners will make good use of the Socratic method in a collaborative task that begins with an assumed solution and ends with deeper understanding of the idea of determining two triangles congruent.
Curated OER
The Truth About Triangles And Proofs
Students engage in a lesson that is about the classification of triangles and the mathematical proofs involved in working with them. They work on a variety of problems that are created by the teacher with the focus upon the importance of...
Curated OER
Similar triangles
Tenth graders investigate the theorems of ASA, AAS, AAA and ASA. In this geometry lesson, 10th graders discuss the theorems of triangles and how it is used to solve for missing sides or angles. They review how two angles are formed by...
Curated OER
SAS Similarity Theorem
Students identify and use the similarity theorem. In this geometry lesson, students differentiate between congruent and similar triangles. They solve problems using the computer modifying shapes by dragging.
Curated OER
Triangle Congruence
Learners use web applet to create congruent triangles. For this geometry lesson, students differentiate between congruent and similar. They create shapes online and drag those shapes around to create visuals of triangles.
Curated OER
Congruent Triangles
Students identify properties of triangles. For this geometry lesson, students differentiate between similar and congruent triangles. They use the umber of sides to help define the angle of the polygon.
Illustrative Mathematics
Why Does SSS Work?
While it may seem incredibly obvious to the geometry student that congruent sides make congruent triangles, the proving of this by definition actually takes a bit of work. This exercise steps the class through this kind of proof by...
Curated OER
Similarity and Congruence
Students explore the concept of similarity and congruence. In this similarity and congruence lesson, students cut out strips of paper and form a triangle. Students try to prove that their triangles are congruent using the SSS theorem of...
Curated OER
Why can't We Use SSA to Prove Triangles Congruent?
Students investigate triangles and congruences. In this geometry lesson, students differentiate between inductive and deductive reasoning. They differentiate between similar and congruent triangles.
Curated OER
CSI Investigation of Congruence and Similarity
Students differentiate between similarity and congruence using polygons. In this geometry lesson, students label triangles based on their properties. They find missing sides and angles using the interior sum theorem.
Curated OER
Whatcha Gunna Do When the Hulkster's Measuring Too??
Students measure using tools they have made. For this algebra lesson, students measure the height and distance using non-traditional measuring methods. They apply their findings to algebra and trigonometry properties of measurements.
Curated OER
Why Doesn't SSA Work?
Students investigate the relationship between angles and their sides. In this geometry lesson, students prove why SSA does not work as a true angle side relationship theorem.