Lesson Plan
EngageNY

The Angle-Angle (AA) Criterion for Two Triangles to Be Similar

For Teachers 9th - 10th Standards
What do you need to prove triangles are similar? Learners answer this question through a construction exploration. Once they establish the criteria, they use the congruence and proportionality properties of similar objects to find...
Lesson Plan
EngageNY

The Side-Angle-Side (SAS) and Side-Side-Side (SSS) Criteria for Two Triangles to Be Similar

For Students 9th - 10th Standards
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...
Lesson Plan
EngageNY

Special Relationships Within Right Triangles—Dividing into Two Similar Sub-Triangles

For Students 9th - 10th Standards
Why are right triangles so special? Pupils begin their study of right triangles by examining similar right triangles. Verifying through proofs, scholars recognize the three similar right triangles formed by drawing the altitude. Once...
Lesson Plan
EngageNY

Incredibly Useful Ratios

For Students 9th - 10th Standards
Start the exploration of trigonometry off right! Pupils build on their understanding of similarity in this lesson plan that introduces the three trigonometric ratios. They first learn to identify opposite and adjacent...
Lesson Plan
EngageNY

The Definition of Sine, Cosine, and Tangent

For Students 9th - 10th Standards
Introduce your classes to a new world of mathematics. Pupils learn to call trigonometric ratios by their given names: sine, cosine, and tangent. They find ratios and use known ratios to discover missing sides of similar...
Lesson Plan
EngageNY

Sine and Cosine of Complementary Angles and Special Angles

For Students 9th - 10th Standards
Building trigonometric basics here will last a mathematical lifetime. Learners expand on the previous lesson in a 36-part series by examining relationships between the sine and cosine of complementary angles. They also review the...
Lesson Plan
EngageNY

Trigonometry and the Pythagorean Theorem

For Students 9th - 11th Standards
Ancient Egyptians sure knew their trigonometry! Pupils learn how the pyramid architects applied right triangle trigonometry. When comparing the Pythagorean theorem to the trigonometric ratios, they learn an important connection that...
Lesson Plan
EngageNY

Using Trigonometry to Find Side Lengths of an Acute Triangle

For Students 9th - 10th Standards
Not all triangles are right! Pupils learn to tackle non-right triangles using the Law of Sines and Law of Cosines. After using the two laws, they then apply them to word problems. 
Lesson Plan
EngageNY

Three-Dimensional Space

For Teachers 9th - 10th Standards
How do 2-D properties relate in 3-D? Lead the class in a discussion on how to draw and see relationships of lines and planes in three dimensions. The ability to see these relationships is critical to the further study of volume and...
Lesson Plan
EngageNY

Thales’ Theorem

For Teachers 9th - 10th Standards
Isn't paper pushing supposed to be boring? Learners attempt a paper-pushing puzzle to develop ideas about angles inscribed on a diameter of a circle. Learners then formalize Thales' theorem and use geometric properties to develop a proof...
Lesson Plan
EngageNY

Ptolemy's Theorem

For Teachers 9th - 12th Standards
Everyone's heard of Pythagoras, but who's Ptolemy? Learners test Ptolemy's Theorem using a specific cyclic quadrilateral and a ruler in the 22nd installment of a 23-part module. They then work through a proof of the theorem.
Lesson Plan
EngageNY

Special Lines in Triangles (part 1)

For Students 9th - 10th Standards
Allow your pupils to become the mathematicians! Individuals explore the properties of a midsegment of a triangle through construction and measurement. Once they figure out the properties, learners use them to draw conclusions.
Lesson Plan
EngageNY

Review of the Assumptions (part 1)

For Students 9th - 10th Standards
What was the property again? Tired of hearing this from your pupils? Use this table to organize properties studied and as a reference tool for individuals. Learners apply each property in the third column of the table to ensure their...
Lesson Plan
EngageNY

Triangle Congruency Proofs (part 2)

For Teachers 9th - 10th Standards
Looking to challenge your young scholars 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...
Lesson Plan
EngageNY

Equations for Lines Using Normal Segments

For Students 9th - 12th Standards
Describing a line using an algebraic equation is an essential skill in mathematics. The previous lesson in the series challenged learners to determine if segments are perpendicular with a formula. Now they use the formula to...
Lesson Plan
EngageNY

Rotations, Reflections, and Symmetry

For Teachers 9th - 10th Standards
Lead your high school class on a journey through the world of symmetry and reflections as you discuss geometric principles. Pupils differentiate between reflections and rotations, explore rotational symmetry, and investigate how to...
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

Scale Factors

For Students 9th - 10th Standards
Is it bigger, or is it smaller—or maybe it's the same size? Individuals learn to describe enlargements and reductions and quantify the result. Lesson five in the series connects the creation of a dilated image to the result. Pupils...
Lesson Plan
EngageNY

Dilations as Transformations of the Plane

For Teachers 9th - 10th Standards
Compare and contrast the four types of transformations through constructions! Individuals are expected to construct the each of the different transformations. Although meant for a review, these examples are excellent for initial...
Lesson Plan
EngageNY

How Do Dilations Map Segments?

For Students 9th - 10th Standards
Do you view proofs as an essential geometric skill? The resource builds on an understanding of dilations by proving the Dilation Theorem of Segments. Pupils learn to question and verify rather than make assumptions. 
Lesson Plan
EngageNY

How Do Dilations Map Lines, Rays, and Circles?

For Students 9th - 10th Standards
Applying a learned technique to a new type of problem is an important skill in mathematics. The lesson plan asks scholars to apply their understanding to analyze dilations of different figures. They make conjectures and conclusions...
Lesson Plan
EngageNY

Properties of Similarity Transformations

For Teachers 9th - 10th Standards
You can explain it, but can you do it? After learners view a sequence of transformations, the next logical step is creating the transformation. Challenge your classes to construct a composition of transformations and verify the...
Lesson Plan
EngageNY

Similarity

For Students 9th - 10th Standards
Learn similarity through a transformations lens! Individuals examine the effects of transformations and analyze the properties of similarity, and conclude that any image that can be created through transformations is similar. The...
Lesson Plan
EngageNY

Similarity and the Angle Bisector Theorem

For Teachers 9th - 10th Standards
Identifying and verifying reproducible patterns in mathematics is an essential skill. Mathematicians identify the relationship of sides when an angle is bisected in a triangle. Once the pupils determine the relationship, they prove it to...

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