Lesson Plan
Illustrative Mathematics

Lines of Symmetry for Triangles

For Teachers 3rd - 5th Standards
What can symmetry tell us about triangles? After looking at four examples, learners will come to realize that lines of symmetry are different for equilateral, isosceles, and scalene triangles. Use this guided practice activity as an...
Worksheet
Savvas Learning

Colorful Triangles

For Students 4th - 5th Standards
Learners examine a figure made up of different types of triangles and then determine whether each triangle is right, acute, or obtuse. Next, they color each type of triangle a different color. Finally, pupils answer three fill in the...
Worksheet
Curated OER

Classifying Triangles Using Sides

For Students 4th - 5th
In this geometry learning exercise, students answer 8 fill in the blank questions where they must examine 5 different complex geometric figures to classify triangles.
Handout
McGraw Hill

Triangles

For Students 4th - 7th Standards
After reviewing characteristics of seven types of triangles, young geometers discover how to find the missing angle of a triangle. Then, they practice identifying triangles, find missing angles, and find missing side lengths of...
Worksheet
Curated OER

Triangles

For Students 4th - 7th Standards
Why are there so many different types of triangles? Be that as it may, beginning geometers need to understand the differences between equilateral, isosceles, scalene, and right triangles, and they get a visual approach with this...
Worksheet
Curated OER

To Be a Triangle Or Not To Be a Triangle?

For Students 10th
In this triangles worksheet, 10th graders solve and complete 10 different problems that include applying the Triangle Inequality Theorem. First, they use the illustrated triangles and the data table to test the theorem. Then, students...
Worksheet
Curated OER

Classification of Triangle Measurement & Perimeter

For Students 10th
In this classification of triangles worksheet, 10th graders identify and complete 8 different problems that include determining the measurement and perimeter of various types of triangles. First, they color all right, acute, and obtuse...
Instructional Video6:29
Corbett Maths

Pythagoras Rectangles and Isosceles Triangles

For Students 7th - 12th Standards
When does the Pythagorean Theorem come in handy? An intriguing video uses the Pythagorean Theorem to solve problems other than simply finding the length of a side of a right triangle. Pupils find the diagonal of a rectangle and the...
Assessment
Concord Consortium

Isosceles Triangle Spaces

For Students 7th - 10th Standards
How many different types of triangles can your class name? A discovery lesson guides learners through an exploration of the different triangle types and the relationships between their angles and sides. Using coordinate geometry,...
Worksheet
Curated OER

Types of Triangles

For Students 2nd - 4th
Young math whizzes solve four problems in which a triangle with labeled angle measurements is analyzed. They mark if each triangle is acute, right, or obtuse.
Organizer
Curated OER

Triangles

For Students 3rd - 7th
In this geometry learning exercise, students will answer questions to determine if a shape is a triangle and if so, what type of triangle.
Worksheet
Mt. San Antonio Collage

Inequalities in a Triangle

For Students 9th - 12th Standards
Stuck with triangle proofs? Take a 180° and provide learners with a guided worksheet that tests their knowledge with triangle inequalities. The questions require different types of proofs that range in levels of difficulty. 
Lesson Plan
National Security Agency

Classifying Triangles

For Teachers 4th - 8th Standards
Building on young mathematicians' prior knowledge of three-sided shapes, this lesson series explores the defining characteristics of different types of triangles. Starting with a shared reading of the children's book The Greedy...
Lesson Plan
Digging Into Math

Classifying Triangles

For Teachers 4th - 8th Standards
Young mathematicians explore the world of three-sided shapes in this lesson on the different types of triangles. Starting with a general introduction to classification using Venn diagrams, children learn how to categorize triangles...
Worksheet
Curated OER

Triangle Designs

For Students 4th - 6th
In this triangles worksheet, students draw different triangles and write how many sides and angles each one has. Students draw 4 kinds of triangles and have 2 that are impossible to draw.
Worksheet
Curated OER

Learning About Triangles

For Students 4th - 6th
Upper graders label four triangles and fill in the labels correctly. They draw three original triangles and answer the questions about them.
Worksheet
Curated OER

Countdown Challenge: Triangle Inequality Theorem

For Students 7th - 8th
For this triangle inequality worksheet, students test the Triangle Inequality Theorem. They measure the sides of given triangles, identify the type of triangle, and name angles in the triangle. The one-page worksheet contains 36 problems.
Assessment
Bowland

Rods and Triangles

For Teachers 6th - 9th
Scholars explore triangles with rods of different lengths. Using rods of 2, 4, 6, 8, and 10 cm class members build as many different types of triangles as they can. They also describe properties of these triangles and determine...
Assessment
Concord Consortium

Triangles: Angle Space

For Students 9th - 12th
Three angles in a triangle, three-dimensional space, it all seems connected somehow. Given several different triangles, pupils use the three angles of the triangle as coordinates to plot points in three-dimensional space. They explore...
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...
Worksheet
Curated OER

Triangles

For Students 10th
In this triangles instructional activity, 10th graders solve 3 extensive informal geometry problems that involve triangles. First, they sketch a triangle, selecting 3 of the sides and constructing 3 midpoints. Students then draw each of...
Worksheet
Curated OER

Classifying Triangles

For Students 6th
In this classifying triangles worksheet, 6th graders write the type of triangle, acute, right or obtuse, for 9 pictures of triangles, answers included.
Assessment
Concord Consortium

Always, Sometimes, Never

For Students 9th - 10th Standards
Do your learners always, sometimes, or never remember the properties of the segments in triangles? Get that number closer to always with a creative lesson analyzing all four segments. Scholars consider a statement about one of the...
Worksheet
Curated OER

Triangles

For Students 10th
In this triangles worksheet, 10th graders solve 12 different problems that include various angles of triangles. First, they determine the measure of an exterior angle. Then, students determine the measure of any of the base angles of an...

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