Mt. San Antonio Collage
Isosceles Triangles and Special Line Segments
Under which conditions can a triangle be classified as isosceles? High schoolers practice identifying isosceles triangles and special line segments, including angle bisectors, medians of triangles, and perpendicular bisectors of sides of...
Inside Mathematics
Circles in Triangles
Challenge the class with inscribed circles in triangles. The assessment task requests class members use their knowledge of circles and right triangles to prove two triangles are congruent. They go on to utilize their knowledge of...
GeoGebra
Conjectures and Proof
Transform proofs using triangle rotations. By rotating a triangle around various points, class members develop proofs. Participants prove relationships of alternative interior angles formed by parallel lines and the sum of the interior...
EngageNY
Congruence Criteria for Triangles—SAS
Looking for a different approach to triangle congruence criteria? Employ transformations to determine congruent triangles. Learners list the transformations required to map one triangle to the next. They learn to identify congruence if...
EngageNY
Unknown Angle Proofs—Proofs of Known Facts
Lead the class in a Greek history activity with a geometric twist. Pupils relate a short video about geometric properties to modern-day methods of solving for unknown angles. They discuss parallel line theorems and complete practice...
EngageNY
Similar Triangles in Circle-Secant (or Circle-Secant-Tangent) Diagrams
First angle measures, now segment lengths. High schoolers first measure segments formed by secants that intersect interior to a circle, secants that intersect exterior to a circle, and a secant and a tangent that intersect exterior to a...
Geometry Accelerated
Accelerated Geometry Review Sheet
Your geometry learners use their knowledge of various geometric concepts to write proofs. Starting with givens containing parallel line segments with transversals and triangles and quadrilaterals, and the mid-point and distance formulas;...
Curated OER
Triangles
In this triangles worksheet, 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 3 medians by...
Curated OER
Polygons
Young scholars investigate the concepts related to the study of polygons. They specifically look at how angles is related. The lesson includes specific examples and dialogue to be used by the teacher during direct instruction and...
Curated OER
The Sum of All Angles
Students add up the different angles using the angle addition postulate. In this geometry lesson, students differentiate between interior and exterior angles. They calculate the different angles for triangles and use proof to show their...
Curated OER
The Truth About Triangles And Proofs
Learners engage in a lesson that is about the classification of triangles and the mathematical proofs involved in working with them. They work on a variety of problems that are created by the teacher with the focus upon the importance of...
Curated OER
Interior/Exterior Polygon Angles and Tessellations
Students discover the sum of the interior and exterior angles of several polygons. In this Geometers sketchpad lesson plan, students work in groups to find the stated measurements of triangles, quadrilaterals, pentagons and hexagons....
Mathematics Vision Project
Module 3: Geometric Figures
It's just not enough to know that something is true. Part of a MVP Geometry unit teaches young mathematicians how to write flow proofs and two-column proofs for conjectures involving lines, angles, and triangles.
Utah Education Network (UEN)
Geometric Figures and Scale Drawings
Scale up your lessons on geometry and ask learners to investigate conditions on triangles, scale drawings, the area and circumference of circles, and angle relationships. The resource includes activities and a homework assignment.
Curated OER
Formula Determination
Students derive a formula for the interior degrees in any convex polygon. In this geometric figure activity, students determine the shapes of various polygons and the number of triangles formed. They use this information to derive the...
Curated OER
Angle-Side Relationships
Students calculate the different sides and angles of a triangle. For this geometry lesson, students use triangular properties to define the relationship between two triangle. They identify missing angles using the interior angle theorem.
Curated OER
Find Missing Angles of Triangles
In this triangles instructional activity, students find the missing angles of a set of 4 triangles. Answers are included on page 2.
Corbett Maths
Hexagon Inscribed Within a Circle
Mark off the length of the radius around the circle. Using a compass, the presenter shows how to construct a regular hexagon in a circle. Pupils see how triangles formed in the hexagon are equilateral, allowing for the construction to...
Curated OER
Identifying Triangles
Sixth graders identify and define a variety of triangles. In this identification of triangles lesson, 6th graders draw examples of each triangle on a whiteboard, then complete a worksheet.
Curated OER
Triangle Inequalities
In this triangle inequalities worksheet, 10th graders solve 10 different problems that include various types of triangles. First, they determine which side is the longest side of a triangle with given the exterior angle measurement....
Curated OER
Interior and Exterior Angles
In this interior and exterior angles worksheet, 10th graders solve 10 different problems that include determining the interior and exterior of various triangles. They determine the measure of an exterior angle and then they determining...
Curated OER
Triangle Inequality Theorem
Students 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...
Curated OER
Geometric Properties
Students find triangular angles using the angle theorem. In this geometry instructional activity, students describe labeled triangles, use the pythagorean theorem, and rewrite information about triangles in standard form.
Charleston School District
Pre-Test Unit 2: Similar and Congruent
A pre-test contains questions about transformations that lead to congruent and similar images. It also covers angle relationships associated with triangles and parallel lines intersected by a transversal.