One of TI-Nspire’s most powerful features is its ability to grab and move objects, enabling you to observe changes happening dynamically in real time. This is especially true of constructions, including those containing measurements and calculations.

Did you notice what happens when you drag a point on a ray? Try moving it both above and below the line. The angle changes, but it never gets larger than 180 degrees.

TI-Nspire can only measure angles that are 180 degrees or less (without help from advanced authors). The Redefine tool is very helpful, especially if you begin making a geometric construction without thinking through each step in advance.

Using the Redefine tool to put the moveable point on a circle arc has some nice benefits. Placing the point on the circle arc will limit where you can drag the point; the point will follow the smooth path of the circle arc as it is dragged. Taking the time to perform this behind-the-scenes work will make your constructions look and feel more professional. Here are the steps to redefine a point:

Press [MENU]→Actions→Redefine. [CLICK] the point on the ray, and then [CLICK] the circle arc.

Hover over the circle arc and right-click, [CLICK][MENU]→Hide. Repeat this step to hide the point you used to define the arc.