With TI-Nspire's Length Measurement tool, you can measure the perimeter of a polygon, the circumference of a circle, the length of a segment, or the distance between any two points. For this example, you will construct an equilateral triangle ABC with side lengths of 10 inches.

First, draw a horizontal segment on a new Geometry page. Press **[CTRL][DOC]**→Add Geometry and then press **[MENU]**→Points & Lines→Segment to access the Segment tool. Follow these steps to measure the length of the segment:

Press [MENU]→Measurement→Length to open the Length Measurement tool.

Move your cursor to the object being measured and press [CLICK].

To find the distance between two points, click each endpoint once to get the measurement to pop up.

Use the Touchpad to move the measurement to a desired location and press [CLICK] or press [ENTER] to drop it in place.

Press [ESC] to exit the Length Measurement tool.

By default, the scale is given in centimeters and is located in the upper-right corner of the screen.

Have you noticed that you have many clickable areas on the TI-Nspire? The scale behaves much like a text box. To change units, click the scale once and press the **[DEL]** key to delete the current unit. Type a new unit using the alpha keys, and press **[ENTER]** to complete the task.

All existing length and area measurements are automatically updated to reflect this change. For this task, the sides of the equilateral triangle are measured in inches.

The second screen shows the result of changing the scale from centimeters to inches.

The length of the segment that you measured is also a clickable area. Try double-clicking the length measurement and changing it to 10 in. See the third screen.