Four triangles are depicted for learners to construct on a geoboard. They compute and compare the areas, and so meet one of the sixth grade Common Core standards for geometry. Note that the set of triangles does not include a right...

This comprehensive web lesson describes how to classify triangles by their angle and side measurements. It provides real-world examples and exercises for students to practice the skill.

This site has an activity that displays several impossible triangles. The rules for triangles are also displayed. The student has to determine which rule has been violated for each impossible triangle.

Students explore four types of angles in this interactive web lesson.