Need an activity for teaching the Pythagorean Theorem? Geometry juniors apply the Pythagorean theorem to two triangles to determine a final calculation. 

Geometers explore symmetries of isosceles triangles by using rigid transformations of the plane. They complete four tasks, including congruence proofs, which illustrate the relationship between congruence and rigid transformations. The...

Inscribing a square in a circle brings up a number of interesting geometry topics including triangle congruence and how to prove a quadrilateral is a square. This activity is followed up by finding the area of the square and determining...

Learners investigate the symmetries of a convex quadrilateral in a collaborative activity. Rigid motion and complements are explored as learners analyze different cases of reflections across a line.

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 is a "three star" geometry problem where prior knowledge of probability is required to solve this "Tick Tock Triangle" problem, have fun!

This site contains a wealth of problems that deal with the basic definitions of medians, altitudes, angle bisectors, and perpendicular bisectors or the defining characteristics of the different types of triangles. There are also...

Are you looking for a very basic website that will explain the basic properties of a triangle? Use this site to learn about the properties of equilateral triangles, isosceles triangles, right triangles,and scalene triangles. There are...

This is a "three star" geometry problem where prior math problem skills and proof experience is recommended to solve this "Perpendicular Construction" problem.

This geometry lesson defines equilateral, isosceles, and scalene triangles, and has a variety of exercises, including drawing exercises.

On this site students are instructed to locate different types of polygons on triangle grid paper. This page can be printed so that students can actually draw them. It also gives a definitions link for each polygon.