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.
Lesson Plan
Curated OER

Geometric Figures-Triangles

For Teachers 4th
Fourth graders explore triangles. In this math instructional activity, 4th graders discuss the different types of triangles. Students create triangles using wiki sticks. Students complete an online matching game.
Lesson Plan
Curated OER

Isosceles Triangle Theorem

For Teachers 8th - 10th
In this geometry worksheet, students differentiate between regular triangles and isosceles triangles. They apply the converse theorem and the vertex angle. There are eleven questions with an answer key.
Worksheet
Curated OER

Area of Triangles - Word Problems

For Students 5th - 7th
Here is an area of triangles practice activity in which learners sharpen their problem solving skills as they solve six story problems.
Worksheet
Curated OER

Attributes of Shapes Guided Lesson Explanation

For Students 1st
Triangles, circles, and rectangles are featured in a colorful, one-page worksheet that defines and illustrates these shapes. Read the explanations with your first graders and have them count the number of shapes in a given box. Since the...
Lesson Plan
Curated OER

Circles, Squares, Triangles and Rectangles In Our World

For Teachers Pre-K - 2nd
Here is an engaging geometry instructional activity which has students identify the properties of shapes and cut shapes out of magazines. They make cookies using cookie cutters in various shapes.
Lesson Plan
Curated OER

You Can't Go Wrong with a Right Triangle 2

For Teachers 3rd - 5th
Upper graders use the properties of right angle trignonmetry to measure objects such as the school flagpole. They solve real world problems using these properties.
Lesson Plan
Curated OER

Investigation Area of Geometric Shapes

For Teachers 4th
Fourth graders use triangle paper to design patterns using geometric figures and find the areas of those figures by counting units. Students are assessed by determining which figure has the greatest area and explaining their reasoning.
Lesson Plan
Improving Measurement and Geometry in Elementary Schools

The Sum of the Interior Angles of a Polygon

For Teachers 4th - 5th Standards
Junior geometers discover that polygons can be decomposed into triangles and that the number of triangles can be determined by a rule. Note that the Geometer’s Sketchpad® software is required to carry out all components of this...
Worksheet
Curated OER

Lengths of Horizontal and Vertical Line Segments

For Students 5th - 7th
Use this lengths of horizontal and vertical line segments practice worksheet to have learners sharpen their problem solving skills as they solve six story problems.
Lesson Plan
Curated OER

The Trapping of Trapezoids

For Teachers 6th - 8th
This is a nice hands-on activity where young geometers create trapezoids and calculate their area by looking at areas of quadrilaterals and triangles. 
Lesson Plan
Curated OER

Analyzing Congruence Proofs

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

Partitioning a Hexagon

For Teachers 7th - 9th Standards
The task at hand is to partition a hexagon into two, four, and eight congruent figures. Make sure to give your wizards a sheet of triangle grid paper on which to decompose the hexagons. Have them explain which rotations, reflections, or...
Lesson Plan
Curated OER

Review Geometry - Week 8 (Triangles)

For Teachers 11th - 12th
In this triangle worksheet, students use similar figures to find the length of one side of two similar triangles. They find the area of a triangle inscribed in a rectangle. This two-page worksheet contains eight problems.
Worksheet
Curated OER

Triangle worksheets

For Students 10th
In this geometry worksheet, 10th graders explore triangle properties, including the sum of the measures of the angles of a triangle, the triangle inequalities, properties of isosceles triangles, properties of congruent triangles, and...
Lesson Plan
Curated OER

Drawing a Triangle with Cabri Junior

For Teachers 9th - 12th Standards
Learners draw triangles on their graphing calculators using the Cabri Junior application. In this graphing calculator lesson, students follow step by step directions to create triangles on their calculator. They identify the type of...
Interactive
Curated OER

Area of Parallelogram and Triangle

For Students 10th
In this geometry instructional activity, 10th graders determine the area of triangles and parallelograms. The one page interactive instructional activity contains ten questions. Answers and hints are included. 
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 lesson, students are given spaghetti of different lengths and asked to create triangles. They conclude the necessary length needed to make a...
Lesson Plan
Curated OER

Pythagorean Theorem Spreadsheet

For Teachers 6th - 8th
Studetns use a spreadsheet to organize data on the sides of a triangle. They use the Pythagorean Theorem and the If then spreadsheet function to decide whether the three sides determine a right triangle. Students work individual...
Lesson Plan
Curated OER

Special Triangles and Circles

For Teachers 9th - 11th
Students investigate special triangles and circles. In this geometry lesson, students construct a perpendicular bisector and discuss angles of a triangle. They find the angle bisectors, vetex and the types of circle constructed.
Lesson Plan
EngageNY

The Side-Angle-Side (SAS) and Side-Side-Side (SSS) Criteria for Two Triangles to Be Similar

For Students 9th - 10th Standards
Playing with mathematics can invoke curiosity and excitement. As pupils construct triangles with given criteria, they determine the necessary requirements to support similarity. After determining the criteria, they practice...
Lesson Plan
Illustrative Mathematics

All vs. Only Some

For Teachers Pre-K - 2nd Standards
All shapes have certain defining attributes that set them apart from others. In order to understand this, young mathematicians look at examples and non-examples of triangles, rectangles, and squares, working as a whole class to create...
Lesson Plan
EngageNY

Pythagorean Theorem, Revisited

For Students 8th Standards
Transform your pupils into mathematicians as they learn to prove the popular Pythagorean Theorem. The 16th lesson plan in the series of 25 continues by teaching learners how to develop a proof. It shows how to prove the Pythagorean...
Activity
Illustrative Mathematics

Congruent Triangles

For Teachers 7th - 9th Standards
Geometers prove that triangle PQR is congruent to triangle ABC by describing any combination of rotations, reflections, and translations that would prove it so. There is only this single task on the handout, but a detailed explanation of...

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