Education Technology

Constructing a Pentagon, An Alternative Method

Published on 05/09/2010

Activity Overview

Use the TN-Nspire (OS 2.0) to construct a regular pentagon using lines, rays, line segments, and circles of various diameters. The characteristics of a regular pentagon are discussed and used to verify the construction meets the criteria of all sides being equal, and all angles being equal. The measurement feature of the TI-Nspire is used to verify angle measurements, while circles verify sides are congruent.

Before the Activity

Download and make copies of word document for teacher and/or students to use. It is detailed enough for students to use for self discovery.

A Video is available, but too large to upload to TI website (8MB) It is available at

During the Activity

I suggest you use the smaller circle, and line from bottom through left midpoint. Hide to make construction easier and less confusing.

After the Activity

Follow through in verifying all the angles are equal, and all sides are equal. Note: to increase decimals for the angle measurement, place cursor on the number (text) and press "+", to decrease, press "-". Also suggest use the settings for "Graphs & Geometry" to change from radians (default) to degrees. Be sure to change for Geometry Angle.