Solution 22550: Finding the Circumference of a Circle or the Perimeter of a Shape Using the TI-Nspire™ Family Products.
How do I find the circumference of a circle or the perimeter of a shape using the TI-Nspire Family Products?
While there is not a "circumference" tool or a "perimeter" tool on the TI-Nspire family products, these measurements can be found by using the "Length" tool. The Length tool is one of the options under the "Measurement" menu.
Please Note: Texas Instruments recommends all TI-Nspire family users update the handheld and computer software to the latest operating system. More information on the latest operating system can be found at the TI-Nspire CX and TI-Nspire CX CAS latest software pages.
Follow the example listed below to find the circumference of a circle using the TI-Nspire family products:
1) To insert the Geometry application, press [home]  .
2) To begin creating a circle, press [menu]  .
3) The handheld will prompt for a "center point" for the circle. Using the arrow keys, move the cursor to the desired location and press [enter] to set the center point.
4) Use the arrow keys to "expand" or "contract" the circle. When the circle reaches a desirable size, press [enter] to complete the construction. Press [esc] to exit the circle tool.
5) With the circle constructed, press [menu]   to select the "Length" tool.
6) If the cursor is not on the circle, use the arrow keys and move the cursor to any point on the circle. When the circle is "bold", this means it has been selected.
7) A "ghost" of the circumference measurement value will be displayed. Press [enter] to set the circumference value.
8) If desired, use the arrow keys to move the circumference value away from the constructed circle. Finally, press [enter] to paste the circumference value into the Geometry application. Press [esc] to disable the Length tool.
Please Note: The same steps can be applied to find the perimeter of an shape. For example, if the user constructs a rectangle, the "Length" tool, when used, will calculate the perimeter of the constructed rectangle.
Please see the TI-Nspire family guidebooks for additional information.