+
Interactive
Shodor Education Foundation

Squaring the Triangle

For Students 8th - 12th Standards
Teach budding mathematicians how to square a triangle with an interactive that shows a graphical proof of the Pythagorean Theorem. Pupils alter the lengths of the legs using sliders. Using the inputted lengths, the applet displays the...
+
Worksheet
Curated OER

Angles Activities

For Students 5th - 8th
A series of geometry worksheets have mathematicians constructing, dissecting, overlapping, and measuring as they analyze angles in various contexts. Learners use symmetry and reflections in a compass rose to write instructions on...
+
PPT
Curated OER

Isosceles Triangles

For Teachers 4th - 5th
In need of a fun way to define an isosceles triangle? This activity has learners fold a paper in half and then cut it to create an isosceles triangle. They determine the line of symmetry by folding the triangle in half and then use the...
+
Lesson Plan
Curated OER

Exploring Polygons and The Greedy Triangle

For Teachers 1st - 3rd
Excellent lesson plan! Anne Linehane's geometry story, The Greedy Triangle, offers an opportunity to practice forming various types of polygons with your learners. Using elastic bands (or Chinese jump ropes),...
+
Lesson Plan
Virginia Department of Education

How Many Triangles?

For Teachers 9th - 11th Standards
Something for young mathematicians to remember: the sum of any two sides must be greater than the third. Class members investigates the Triangle Inequality Theorem to find the relationship between the sides of a triangle. At the same...
+
Lesson Plan
Alabama Learning Exchange

Triangle Area: No Height? Use the Sine

For Students 9th - 12th Standards
No height? No problem! Learners use their knowledge and a little help from GeoGebra to develop the Law of Sines formula. The Law of Sines helps to determine the height of triangles to calculate the area.
+
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...
+
Lesson Plan
1
1
Illustrative Mathematics

Right Triangles Inscribed in Circles I

For Teachers 9th - 10th Standards
One of the basic properties of inscribed angles gets a triangle proof treatment in a short but detailed exercise. Leading directions take the learner through identifying characteristics of a circle and how they relate to angles and...
+
Lesson Plan
Illustrative Mathematics

Joining Two Midpoints of Sides of a Triangle

For Teachers 9th - 11th Standards
Without ever using the actual term, this exercise has the learner develop the key properties of the midsegment of a triangle. This task leads the class to discover a proof of similar triangles using the properties of parallel lines cut...
+
Assessment
Mathematics Assessment Project

Circles in Triangles

For Students 9th - 12th Standards
Circles, and triangles, and tangents, oh my! In the assessment task, learners first answer questions leading to the radius of an inscribed circle for a given right triangle. They then use the result to independently determine the radius...
+
Interactive
DocsTeach

Analyzing Photographs of the Triangle Shirtwaist Factory Fire

For Teachers 4th - 8th Standards
While a catalyst for the labor movement, 146 people lost their lives in the Triangle Shirtwaist Factory Fire in 1913. A series of photographs of the aftermath of the tragedy help young historians consider the impact of the fire. The...
+
Lesson Plan
Curated OER

Triangle Inequality Theorem

For Teachers 9th - 12th Standards
High schoolers investigate the relationship between angle measures and sides of a triangle and the relationships among the three sides of a triangle. The use of technology (Cabri, Jr.) allows learners to make and test conjectures as they...
+
Lesson Plan
Curated OER

Special Right Triangles

For Teachers 9th - 12th Standards
Using the Pythagorean Theorem to solve for missing angles, students evaluate right triangles and their properties.
+
Activity
Curated OER

Triangle Series

For Teachers 9th - 12th Standards
Your algebra learners emphasize the"geometric" in geometric series as they use a common ratio between algebraic terms and find that it corresponds to a repeated similarity transformation. 
+
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 Triangle,...
+
Worksheet
McGraw Hill

The Wellness Triangle

For Students 6th - 9th
Health is not simply the absence of disease or a one-dimensional notion, but is really a combination of physical, emotional, and social components. Discover the wellness triangle, which not only includes signs of health and ways to...
+
Activity
Teach Engineering

Stay in Shape

For Teachers 7th - 9th Standards
Using their knowledge of right triangles, pupils find out how far a ship is from a light house. Class members determine how far around the world a ship would be sailing at a constant speed.
+
Lesson Plan
Curated OER

Basic Right Triangles

For Teachers 2nd - 4th
Elementary schoolers examine the attributes of triangles. In this triangle lesson plan, learners compare regular triangles and right triangles. They explore vertices and angles and investigate obtuse and acute angles. Pupils draw...
+
Lesson Plan
Curated OER

Solving Problems Using Triangle Inequality Theorem

For Teachers 6th
Sixth graders investigate triangles and the inequality theorem. They will collaborate in groups to determine the length of a longest side of a triangle. Then relate the size of the triangle to its angles using protractors, yard sticks,...
+
Lesson Plan
Curated OER

Triangle Inequality

For Teachers 4th - 6th
Learners discover that the sum of the lengths of any two sides of a triangle must be greater than the third side. They are shown how a triangle is formed using three strips such as that the triangle is seen inside the strips.
+
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.
+
Lesson Plan
Curated OER

Pascal's Triangle

For Teachers 7th - 11th
Students explore the concept of Pascal's Triangle. In this Pascal's Triangle lesson, students use an applet called 'Coloring Multiples' to explore Pascal's Triangle. Students develop patterns starting with various numbers in Pascal's...
+
Lesson Plan
Curated OER

Investigation - Looking For Triangles

For Teachers 7th
Seventh graders investigate a series of triangles, looking for patterns and generalizing what they have found. They analyze the pattern data and organize it into a table and graph. Students identify the relationship and discover the rule...

Other popular searches