Have you ever wondered why triangles are used to build bridges, make rafters in buildings, and even make curved domes?

Triangles cannot be deformed.

The only way to change a triangle is by breaking one of its joints or altering a side length.

Many other shapes (including rectangles) do not have this property and can deform if pressure is placed on one of its joints or sides.

A triangle can represent a flat surface.  Since a triangle only requires three points, they are more efficient than rectangles, which require four points, for drawing surfaces.

Also, consider the fact that once a triangle has been drawn, only one more point needs to be stored for each additional connected triangle.

• Discuss how to classify triangles.
• Examine side-angle relationships in triangles.
• Construct \(60^\circ\) angles.

We will continue to build upon our knowledge of triangles and gain more insight into the properties that make triangles so important.