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...
Flipped Math
Intro to Trigonometry
Expand trigonometric ratios beyond right triangles. Pupils start with a review of trigonometric ratios and then take a look at angles in standard position to determine their measurements. Scholars discover how to find coterminal angles...
Curated OER
Similar Right Triangles-Introductions to Trigonometry
In this geometry worksheet, students examine similar right triangles as the basis for the foundation of trigonometry. Students define the basic trigonometric functions and use a calculator to find the trigonometric value of an angle. The...
Curated OER
Similarity
Middle schoolers engage in a lesson that is concerned with the concept of similarity. This takes higher order thinking skills and being able to separate into categories. Specifically in this lesson they are introduced to the scale and...
Curated OER
Triangles
In this triangles learning exercise, students identify 3 triangles by the length of their sides and 3 triangles according to their internal angles.
Curated OER
Similarity and Congruence
Pupils explore the concept of similarity and congruence. In this similarity and congruence lesson, students cut out strips of paper and form a triangle. Pupils try to prove that their triangles are congruent using the SSS theorem of...
Curated OER
Geography: Lengths, Perimeter, and Area of Similar Objects
Sixth graders explore characteristics of similar objects.   Using attribute blocks, they explore the ratios of the perimeter, area and side length in similar shapes.  They calculate and compare the area of shapes.
Curated OER
The Sierpinski Triangle
Students investigate the Sierpinski triangle. In this geometry lesson plan, students define fractal curves and its relationship to triangles. They identify repeating sequences and relate it to fractals.
Curated OER
Similar Figures
In this similar figures learning exercise, students determine area and perimeter of rectangles and triangles, then explain their thinking. Answers included on page 2.
Curated OER
Triangles in Architecture
Students find triangles in the real world. In this geometry lesson plan, students analyze and identify properties of two and three-dimensional objects. They differentiate between similarity and congruence.
Curated OER
Similar Triangles - Geometry Exploration
Eighth graders become engaged in a activity in geometry to improve mathematical skills. They construct triangles, segments, and points using Geometer's Sketchpad to demonstrate how dilations of triangles and rectangles change geometric...
Curated OER
Obtuse Triangles
Fourth graders explore obtuse triangles. In this geometry activity, 4th graders make obtuse triangles with paper and scissors. They determine how to find the center of their triangle.
Curated OER
Recognize Triangles
In this shapes worksheet, students are asked to "colour" all of the triangles they find on the page. There are 10 shapes on the page and 4 are triangles. The second page contains suggestions for teachers on activities with 2-D shapes.
Illustrative Mathematics
Applying the Pythagorean Theorem in a Mathematical Context
Participants who use this resource will apply the Pythagorean Theorem to show whether or not the shaded triangle inscribed in a rectangle is a right triangle. Once all of the sides on the shaded triangle are found, it is important that...
Curated OER
Fractals Teachers' Notes
When you see a flower or a tree in nature do you see the math? This web resource contains many ideas for using fractals in a math class including Sierpinski’s triangle, Koch's Snowflake, and the Jurassic Park Fractal. Additionally, it...
Futures Channel
Folding Circles
Students investigate properties of circles. In this geometry lesson plan, students differentiate between similarity and congruence as they observe polygons. They investigate properties of two and three dimensional shape.
Curated OER
Analyzing Congruence Proofs
Looking at numerous examples of triangles, each with different properties, geometers develop their understanding of congruency. They use the notation of a counter-example to disprove certain conjectures and prove geometric theorems and...
EngageNY
Truncated Cones
Learners examine objects and find their volumes using geometric formulas in the 21st installment of this 25-part module. Objects take the shape of truncated cones and pyramids, and individuals apply concepts of similar triangles to find...
University of Utah
Explore Proportional and Linear Relationships
Progress from proportional relationships to linear functions. Pupils first review concepts of proportionality covered in earlier grades. They then extend these concepts to linear functions, such as determining the slope of a...
Education Institute
Four Mathematics Lessons for Grade 9
These four lesson plans build algebra skills for working with numbers in exponential form and for examining triangles. Be aware that in the text, scientific notation is referred to as index notation and the laws of exponents as the laws...
EngageNY
Mid-Module Assessment Task: Grade 7 Mathematics Module 6
This is a mid-module assessment for the 16th lesson in 29 geometry lessons. Individuals demonstrate their understanding of concepts such as vertical and adjacent angles, constructing geometric figures, and triangle congruence criteria.
Scholastic
Study Jams! Congruent Figures
There is more to congruency than just looking similar. Learn the difference and calculate the matching angles and sides to prove the congruence between figures. Lesson has step-by-step slides and follows with an assessment. 
Willow Tree
Area of Common Geometric Figures
Scholars can use area formulas, but can they apply what they know about area? The lesson challenges learners to think logically while practicing finding area of shapes such as rectangles, circles, parallelograms, triangles, and other...
Radford University
Take a Trip
Leave all your travels needs to the math department. Pupils apply knowledge of triangles to identify a triangular path for a traveler to take. They use a given distance for the second leg of the trip and a constraint on the length of the...
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