Texas Instruments TI-83 PLUS - Manual (Page 223)

TI-83 Plus Draw Instructions 220
Drawing Horizontal and Vertical Lines
Drawing a Line Directly on a Graph
To draw a horizontal or vertical line when a graph is displayed, follow
these steps.
1. Select 3:Horizontal or 4:Vertical from the
DRAW
menu. A line is
displayed that moves as you move the cursor.
2. Place the cursor on the y-coordinate (for horizontal lines) or
x-coordinate (for vertical lines) through which you want the drawn line
to pass.
3. Press Í to draw the line on the graph.
To continue drawing lines, repeat steps 2 and 3.
To cancel Horizontal or Vertical , press ‘ .