Creating Shapes Using Gestures (MathDraw)

The MathDraw tool lets you use touchscreen gestures to create points, lines, circles, and other shapes.

• MathDraw is available in Geometry and Graphing.
• Graphing view when the x scale and y scale are identical. This avoids non-circular ellipses and non-square rectangles appearing as circles and squares.

Note: MathDraw is not available in the 3D Graphing.

Activating MathDraw

1. Tap Add, and then tap .
2. Tap Tools .
3. Tap Actions menu, select MathDraw.

The MathDraw tool appears in the application Toolbar. You can begin using the tool.

Canceling MathDraw

▶ When you have finished using the MathDraw tool, tap the X on the tool.

 

To create a labeled point, tap in an open area.

• If the point is close to an existing line, segment, ray, geometric conic (including circles), or polygon, the point snaps to that object. You can also place a point on the intersection of any two of those types of objects.
• If the point is close to a visible grid location in a Graphs view or Geometry view, it snaps to the grid.

 

To create a line or segment, touch the initial position, and then drag to the end position.

• If the drawn line passes near an existing point, the line snaps to the point.
• If the drawn line starts close to an existing point and ends next to another existing point , it becomes a segment defined by those points.
• If the drawn line is nearly parallel or perpendicular to an existing line, segment, or side of a polygon, it aligns to that object.

Note: The default tolerance for detecting parallel/perpendicular lines is 12.5 degrees. This tolerance can be redefined using a variable named
ti_gg_fd.angle_tol. You can change the tolerance in the current problem by setting this variable in the calculator app to a value in the range 0 through 45 (0=no parallel/perpendicular detection).

 

To create a circle or ellipse, use the touchscreen to draw the approximate shape.

• If the drawn shape is sufficiently circular, a circle is created.
• If the shape is elongated, an ellipse is created.
• If the virtual center of the drawn shape is near an existing point, the circle or ellipse is centered on that point.

 

To create a triangle, draw a triangle-like shape.

• If a drawn vertex is close to an existing point, the vertex snaps to the point.

 

To create a rectangle or square, use the touchscreen to draw the perimeter.

• If the drawn shape is nearly square, a square is created.
• If the drawn shape is elongated, a rectangle is created.
• If the center of a square is close to an existing point, the square snaps to that point.

 

To create a polygon, tap a succession of existing points, ending on the first point you tapped.

 

In the Graphs view, MathDraw attempts to recognize certain gestures as functions for analytic parabolas.

Note: The default step value for quantization of the parabola coefficients is 1/32. The denominator of this fraction can be redefined using a variable named ti_gg_fd.par_quant. You can change the step value in the current problem by setting this variable to a value greater or equal to 2. A value of 2, for example, produces a step value of 0.5.

 

To measure the angle between two existing lines, use the touchscreen to draw a circle arc from one of the lines to the other.

• If the intersection point between the two lines does not exist, it is created and labeled.
• The angle is not a directed angle.

 

To create a point midway between two points, tap point 1, point 2, and then point 1 again.

 

To erase objects, use the touchscreen to drag left and right, similar to the motion of erasing a whiteboard.

• The erasure area is the bounding rectangle of the erasure gesture.
• All point objects and their dependents inside the erasure area are removed.