Interactive
CK-12 Foundation

Angle-Side-Angle Triangles: Caution Tape

For Students 10th - 12th Standards
Don't lose your marbles. Scholars use an interactive to create a triangle that closes off a portion of a sidewalk with loose marbles. The Law of Sines helps them find the side measures of such a triangle.
Lesson Plan
Curated OER

Triangles Inscribed in a Circle

For Teachers 9th - 12th Standards
Are you tired of answers without understanding? Learners can give a correct response, but do they really understand the concept? Have young mathematicians think deeper about linear functions, angles, and formulas in algebra....
Lesson Plan
Curated OER

Similar Triangles - Applied Problems

For Teachers 9th - 12th
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.
Lesson Plan
Curated OER

Similar Triangles

For Teachers 9th - 10th
Students differentiate between similar and congruent triangles. In this geometry lesson, students identify the missing side and angle of a triangle. They identify the different ratio and proportion of the sides of a triangle.
Lesson Plan
Curated OER

Similar Triangles

For Teachers 9th
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.
Lesson Plan
Curated OER

Tennis Triangle

For Teachers 9th - 12th
Learners calculate the height of a tree or flagpole. They measure the shadow of the tree or flagpole and the length of a shadow of a meterstick. Using similar triangles, calculate the heigh. Devise two additional ways in which to measure...
Worksheet
Curated OER

Identifying Similar Triangles

For Students 10th
For this identifying similar triangles worksheet, 10th graders solve 5 different proofs related to similar triangles. First, they identify the similar triangles in each figure and explain why they are similar, using the information to...
Interactive
Curated OER

Similar Triangles Multiple Choice

For Students 8th - 10th
In this triangle relationships worksheet, students identify measurements in similar and congruent triangles. Each problem features a drawing of two or more triangles. Students identify missing measurements. There are 5 multiple choice...
Lesson Plan
Curated OER

Identify Similar Figures

For Teachers 6th - 7th
Students explore the concept of similar figures. For this similar figures lesson, students develop the idea that similar figures are a different size but the same shape by comparing similar rectangles. Students use patty paper to trace...
Lesson Plan
Utah Education Network (UEN)

Finding Missing Lengths of Similar Triangles

For Teachers 7th - 10th
Middle and high schoolers explore the properties of similar triangles. In this geometry lesson, pupils play a similarity basketball game, sketch similar triangles, and find the missing measures of similar figures. They find the height of...
Worksheet
Curated OER

Circles: Geometry Review Worksheet

For Students 10th Standards
Tenth graders solve and complete 14 different geometry problems. First, they find the area and circumference of a circle with a given radius. Then, they find the area between a circle and an inscribed equilateral triangle given the...
Worksheet
Curated OER

Identify Similar Triangles With Proofs

For Students 10th - 12th
In this similar triangle instructional activity, students write a two-column proof to explain why determined triangles are similar. Given some line lengths and angle measurements, students use proofs to identify the ratio of specified...
Worksheet
Curated OER

Mid-Segment of a Triangle

For Students 10th - 11th
In this triangle worksheet, students examine triangle diagrams. They determine the perimeter, length of a line, midpoint of a line, and angle measurement from given information. This one-page worksheet contains ten problems.
Lesson Plan
Curated OER

Corresponding Parts of Similar Triangles

For Teachers 9th - 12th Standards
Here is a lesson that has learners take a look at corresponding parts of similar triangles, ratios of similarity, reductions and enlargements. They'll manipulate the scale factor (r) to observe the changes in similar triangles and then...
Lesson Plan
Curated OER

Angles and Similarity

For Teachers 9th - 12th Standards
Students identify triangles as similar or congruent. For this geometry lesson, students drag triangles around on the navigator to see the effect of different angles on the shape of the triangle. They discuss angle similarity and angle...
Lesson Plan
Curated OER

Ratios of Similar Figures

For Teachers 9th - 12th Standards
Students identify the ratios of different triangles. In this geometry lesson, students identify the similarity and differences of triangles. They use the navigator to move the sides of the triangle around.
Lesson Plan
Curated OER

Triangle Inequality Theorem

For Teachers 8th - 10th
Learners use the inequality theorem to solve triangles and their properties. In this geometry instructional activity, students are given spaghetti of different lengths and asked to create triangles. They conclude the necessary length...
Assessment
Inside Mathematics

Hopewell Geometry

For Teachers 9th - 12th Standards
The Hopewell people of the central Ohio Valley used right triangles in the construction of earthworks. Pupils use the Pythagorean Theorem to determine missing dimensions of right triangles used by the Hopewell people. The assessment task...
Lesson Plan
Curated OER

Reflections and Equilateral Triangles

For Teachers 9th - 10th Standards
Your learners collaboratively find the lines of symmetry in an equilateral triangle using rigid transformations and symmetry. Through congruence proofs they show that they understand congruence in terms of rigid motions as they...
Lesson Plan
EngageNY

What Are Similarity Transformations, and Why Do We Need Them?

For Students 9th - 10th Standards
It's time for your young artists to shine! Learners examine images to determine possible similarity transformations. They then provide a sequence of transformations that map one image to the next, or give an explanation why it is...
Activity
Curated OER

Unit Squares and Triangles

For Teachers 9th - 11th Standards
This is an interesting geometry problem. Given the figure, find the area of a triangle that is created by the intersecting lines. The solution requires one to use what he/she knows about coordinate geometry, as well as triangle...
Assessment
EngageNY

End-of-Module Assessment Task - Geometry (module 2)

For Students 9th - 10th Standards
Increase the level of assessment rigor with the test of performance tasks. Topics include similar triangles, trigonometric ratios, Law of Sines, Law of Cosines, and trigonometric problem solving. 
Lesson Plan
EngageNY

How Far Away Is the Moon?

For Students 9th - 10th Standards
Does the space shuttle have an odometer? Maybe, but all that is needed to determine the distance to the moon is a little geometry! The lesson asks scholars to sketch the relationship of the Earth and moon using shadows of an eclipse....
Interactive
CK-12 Foundation

Logarithms: Logarithm Triangle

For Students 10th - 12th Standards
Study logarithmic properties using a triangle. A clever manipulative shows how a triangle can represent the three parts of a logarithmic or exponential equation. Pupils review the concept and then answer guiding questions to further...

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