Isn't paper pushing supposed to be boring? Learners attempt a paper-pushing puzzle to develop ideas about angles inscribed on a diameter of a circle. Learners then formalize Thales' theorem and use geometric properties to develop a proof...

Learners explore Pythagoras and the history behind his theorem. They work together to solve a proof that is embedded in the lesson.

We know theorems about circles—now what? Class members prove a theorem, with half the class taking the case where a point is inside the circle and half the class taking the case where a point is outside the circle. The lesson then...

One of the basic properties of inscribed angles gets a triangle proof treatment in a short but detailed exercise. Leading directions take the learner through identifying characteristics of a circle and how they relate to angles and...

Putting a rectangular object into a circular one—didn't the astronauts on Apollo 13 have to do something like this? Learners first construct the center of a circle using perpendiculars. They then discover how to inscribe a rectangle in a...

Learn about Thales' Theorem with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.

Contains a detailed biography and discussion of the contributions of the ancient Greek philosopher Thales. Part of a larger mathematics site, this page focuses primarily on his contributions to Geometry.

In Spanish. In this interactive activity you can understand and know how to apply direct and inverse homothety to simple shapes, apply Thale's theorem, construct similar polygons and work out their related measurements and know how to...

This task provides a good opportunity to use isosceles triangles and their properties to show an interesting and important result about triangles inscribed in a circle with one side of the triangle a diameter. The fact that these...

Contains a concise summary of the life and major contributions of the ancient Greek Thales of Miletus. Also contains a small picture of a statue of Thales and a diagram that explains Thales's theorem.

A short interactive activity to prove that a triangle inscribed in a semicircle is right-angled.

Explains the basic concept of arcs, angles, and sectors with step-by-step instructions and methods for solving specific problems on your own relating to this topic.

In Spanish. In this site the concept of similar figures is introduced with interactive activities.

Explains the basic concept of circles with step-by-step instructions and methods for solving specific problems on your own relating to this topic.

Learn about inscribed angles with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.

A complete reference guide to diameters. It provides definitions, examples, and interactive activities that enhance further explanation. Includes links to related topics.