The observatory in Arecibo, Puerto Rico provides astronomers insights into the structure of our solar system.

Himeji castle in Japan is a marvel of architecture and a startling example of geometry and military science.

In the Canadian Rockies, the Burgess Shale fossils provide a window to prehistoric Earth.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is part of a collection of definitions of geometric theorems and postulates.

This is the Teacher's Guide that accompanies Geometry Applications: Angles and Planes.

This hands-on activity is a companion to the video segment from the Geometry Applications: Angles and Planes video. In particular, it supports the segment on the architecture of Himeji Castle.

This set of tutorials provides 48 examples of angles and how to identify angles by their measurement. NOTE: The download is a PPT file.

In this Slide Show, learn about the geometry of castle construction.

In this tutorial, learn what the Angle Addition Postulate is and how to use it to solve problems.

In this Math Riddles Game, have your students review vocabulary around the topic of angles.

This set of tutorials provides 48 examples of angles and how to identify angles by their measurement.