Radford University
Building a Recreation Center
It's all about location, location, location. Small groups work to find the best spot for a rec center to serve three different communities. Learners construct the inscribed and circumscribed circles of a triangle to find the best place....
EngageNY
The Computation of the Slope of a Non-Vertical Line
Determine the slope when the unit rate is difficult to see. The 17th part of a 33-part series presents a situation that calls for a method to calculate the slope for any two points. It provides examples when the slope is hard to...
Curated OER
Symmetries of a Quadrilateral I
Learners examine the properties of quadrilaterals from the point of view of rigid motion. Different types of quadrilaterals are characterized by their symmetries, so learners explore the symmetries of a described quadrilateral to...
Curated OER
Area of a Triangle
In this geometry worksheet, students solve problems by finding the area of a triangle. They are given the sides and asked to solve using the Pythagorean Theorem. There are 72 problems.
Curated OER
Properties of the Centers of a Triangle
High schoolers investigate properties of the four centers of a triangle and explore a special property of the circumcenter and orthocenter of a triangle. This instructional activity requires the use of Cabri, Jr.
Illustrative Mathematics
Base and Height
It is easy to find the area of a triangle where the base and the height are given. But in this resource, it is up to your geometers to identify the base and height of the triangle. In fact, your pupils will learn that there are three...
EngageNY
Perimeter and Area of Triangles in the Cartesian Plane
Pupils figure out how to be resourceful when tasked with finding the area of a triangle knowing nothing but its endpoints. Beginning by exploring and decomposing a triangle, learners find the perimeter and area of a triangle. They...
Curated OER
Indirect Proof and Inequalities in one Triangle
In this geometry worksheet, 10th graders complete an indirect proof and order the sides or angles of a triangle. Also, students determine if a triangle can have sides with the given lengths. The two page worksheet contains twelve...
EngageNY
Properties of Parallelograms
Everyone knows that opposite sides of a parallelogram are congruent, but can you prove it? Challenge pupils to use triangle congruence to prove properties of quadrilaterals. Learners complete formal two-column proofs before moving on to...
Shodor Education Foundation
Squaring the Triangle
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...
EngageNY
The Volume Formula of a Pyramid and Cone
Our teacher told us the formula had one-third, but why? Using manipulatives, classmates try to explain the volume formula for a pyramid. After constructing a cube with six congruent pyramids, pupils use scaling principles from...
Curated OER
Triangle's Interior Angles
Given a pair of parallel lines and a triangle in between, geometers prove that the sum of the interior angles is 180 degrees. This quick quest can be used as a pop quiz or exit ticket for your geometry class.
Curated OER
Triangle Problems-Base, Height, and Area
For this geometry worksheet, 10th graders find the base, height, or area of a triangle. The one page interactive worksheet contains ten questions. Answers and hints are included.
Virginia Department of Education
Similar Triangles
Pupils work in pairs to investigate what it takes to prove that two triangles are similar. They work through various shortcuts to find which are enough to show a similarity relationship between the triangles. Small groups work with the...
Hotchalk
Triangle Sum Theorem
Your visual geometry learners will appreciate triangle drawings as they model the triangle sum theorem and algebraically solve to find the missing interior angle in a triangle. Practice problems increase in complexity and vary in their...
Education Development Center
Finding Triangle Vertices
Where in the world (or at least in the coordinate plane) is the third vertex? Given two coordinate points for the vertices of a triangle, individuals find the location of the third vertex. They read an account of fictional...
Radford University
Finding a Location for Your Kitchen Island
Where is the best place to work? Small groups map out a kitchen on a coordinate plane and find the centers of the work triangle to find the best place to install an island. The teams use algebraic methods to locate the center by finding...
Curated OER
Area of Triangle
In this area of a triangle worksheet, students solve 3 problems where they calculate the area of a triangle when they are given the length of the base and the height and the formula.
Curated OER
Orthocenter Of a Triangle
Students find the orthocenter of a triangle. In this geometry lesson, students identify where the altitudes meet in a triangle. They use Cabri software to explore acute, obtuse and right triangles.
Curated OER
To Be a Triangle Or Not To Be a Triangle?
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...
EngageNY
Base Angles of Isosceles Triangles
Build confidence in proofs by proving a known property. Pupils explore two approaches to proving base angles of isosceles triangles are congruent: transformations and SAS. They then apply their understanding of the proof to more complex...
Noyce Foundation
Lyle's Triangles
Try five problems on triangles. Levels A and B focus on shapes that can be created from right triangles. Level C touches upon the relationship between the area of a six-pointed star and the area of each triangle of which it is composed....
Curated OER
Perimeter: The Distance around a Shape
A few good questions move this lesson right along. Young mathematicians use critical-thinking skills as they learn how to determine the perimeter of various shapes. They determine perimeter first by measuring and adding the lengths of...
Curated OER
Midsegments of a Triangle
Students analyze midsegments of triangles in this lesson. They use Cabri Jr. software to observe the relationships between interior angles and midsegments of triangles. Specific instructions for creating this lesson in Cabri Jr. are...
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