# Construct Triangles and Arcs with GeoMaster on the TI-84 Plus

A triangle and an arc are determined by three points, so their construction is much the same. The GeoMaster DRAW menu on the TI-84 Plus calculator offers tools that enable you to construct triangles, arcs, and many other basic geometric shapes. To construct a triangle or an arc, follow these steps:

1. Select the appropriate tool from the DRAW menu.

To do this, press [WINDOW] if the Menu bar is visible at the bottom of the screen or [GRAPH][WINDOW] if it is not. Use

to move the cursor to the tool you want to use and press [ENTER] to select that tool. The tool you selected appears in the upper-right corner of the screen. The first screen illustrates that the Arc tool was selected from the DRAW menu.

2. Use the arrow keys to move the cursor to the location on the screen where you want to construct the first point of the triangle or arc. Press [ENTER] to construct this point.

As you move the cursor, its coordinates are displayed at the bottom of the screen and the anchored point appears in the shape of a diamond, as illustrated in the first screen.

After pressing [ENTER] in this step, you can precisely locate the point by giving the calculator the coordinates of that point. You can also label the point.

3. Use the arrow keys to move the cursor to the location on the screen where you wish to construct the second point defining the triangle or arc. Press [ENTER] to anchor this point.

The second screen illustrates this step when constructing an arc.

4. Use the arrow keys to move the cursor to the location on the screen where you wish to construct the third point defining the triangle or arc. Press [ENTER] to anchor this point.

The third screen illustrates this step when constructing an arc. The arc appears as dashed lines indicating that the construction is not yet complete.

5. Press [ENTER] or move the cursor away from the object.

This is a crucial step. If it is not followed, then the last object you created may vanish when you ask GeoMaster to perform another operation. After doing this step, the figure which appeared as a dashed lines or arcs after performing Step 4 appear as a solid lines or arcs. This indicates that your construction is now housed in the memory of the calculator.

After constructing a triangle or arc, the GeoMaster tool you were using remains active until you deactivate it. So if you want to construct more objects of the same kind, just follow Steps 2 through 5. When you are finished using that tool, you deactivate it by pressing [CLEAR] or by selecting another menu item.

After a triangle or an arc has been constructed, you can move its location on the screen by moving one of the segments defining the triangle or arc, or you can change its shape by moving the points defining the object.