CK-12 Foundation
Ck 12: Geometry: Triangle Classification Grade 8
[Free Registration/Login may be required to access all resource tools.] Classifying triangles by using angle measures and side lengths.
Texas Instruments
Texas Instruments: Similar Figures Discovery Activity
Students can use Cabri Jr. to discover two properties of similar triangles: corresponding angles are congruent and corresponding sides are proportional.
CK-12 Foundation
Ck 12: Interactive Geometry: 6.7 Applications of Similar Triangles
Learn how similar triangles have congruent corresponding angles and proportional corresponding sides.
Shodor Education Foundation
Shodor Interactivate: Lesson: An Introduction to Quadrilaterals
Quadrilaterals-parallelograms, rectangles, and trapezoids-are thoroughly introduced in this lesson plan for upper elementary and middle school learners. Lots of resources are linked to it to help support the teacher and students....
Math Open Reference
Math Open Reference: Triangles
A complete reference guide to types of triangles and triangle perimeter and area. It provides definitions and interactive animated activities that enhance further explanation.
Oswego City School District
Regents Exam Prep Center: Theorems and Postulates for Geometry
Here is a partial list of theorems, postulates, and properties.
Sophia Learning
Sophia: Similarity
This learning tutorial describes the characteristics of similar figures and how to use scale factor and proportions to determine missing side lengths. The lesson includes PowerPoint presentations and videos demonstrating how to solve...
Alabama Learning Exchange
Alex: Tan Ii
The Chinese character mark for Tan II (pronounced she-tow-bah) is the second of two lessons to introduce first grade young scholars to geometry using tangrams. This lesson plan incorporates history, math, and language arts. In this...
Khan Academy
Khan Academy: Similarity and Transformations
Given two polygons, try to map one onto the other using angle-preserving transformations, and determine whether they are similar. Transformations are done in "intuitive mode." Students receive immediate feedback and have the opportunity...
Mocomi & Anibrain Digital Technologies
Mocomi: Types of Triangles
Explore the different types of triangles and other properties.
Texas Education Agency
Texas Gateway: Generalizing Geometric Properties of Ratios in Similar Figures
Students will investigate patterns to make conjectures about geometric relationships and apply the definition of similarity, in terms of a dilation, to identify similar figures and their proportional sides and congruent corresponding...
Cuemath
Cuemath: Triangles
Explore everything about triangles. Learn about the different types, important properties, and how to find its area and perimeter. Check out the solved examples and interactive questions for better understanding.
Texas Education Agency
Texas Gateway: Using Logical Reasoning to Prove Conjectures About Circles
Given conjectures about circles, the student will use deductive reasoning and counterexamples to prove or disprove the conjectures.
Texas Instruments
Texas Instruments: Isosceles Triangle
In this activity, students construct isosceles and equilateral triangles. They discover that if two sides of a triangle are congruent, then the angles opposite them are congruent. They understand that an equilateral triangle is also...
Illustrative Mathematics
Illustrative Mathematics: G Gpe a Midpoint Miracle
In this task, students are asked to draw a quadrilateral so that no two sides are congruent, no two angles are congruent, and no two sides are parallel. The task gives students the opportunity to prove that if we join the midpoints of a...
Illustrative Mathematics
Illustrative Mathematics: 8.g Tile Patterns I: Octagons and Squares
Eighth graders are presented with a tile pattern showing an apparent square surrounded by four octagons. They are asked to answer a question about congruency and angle measurements, as well as prove that the interior shape is really a...
National Council of Teachers of Mathematics
Nctm: Figure This: Math Challenges for Families
Students, teachers, and parents alike will enjoy this challenging math site. It contains a clever brain teaser section plus creative problems related to algebra, geometry, measurement, numbers, statistics, and probability. A Spanish...
Wolfram Research
Wolfram Math World: Rectangle
MathWorld provides the definition of a rectangle and the area formula of a rectangle.
National Institute of Educational Technologies and Teacher Training (Spain)
Ministerio De Educacion: Flecha
Can you make the second arrow the same size as the first? You will be surprised.
CK-12 Foundation
Ck 12: Geometry: Aa Similarity (Intermediate)
[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to identify whether or not two triangles are similar using AA Similarity.
CK-12 Foundation
Ck 12: Interactive Geometry: 6.5 Sss Triangle Similarity
Explore and understand two triangles that are similar.
CK-12 Foundation
Ck 12: Interactive Geometry: 6.4 Sas Triangle Similarity
Explore and understand triangle similarity.
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