Creating Right Triangles in Adobe Illustrator

Here’s a quick way to draw a right triangle in Adobe Illustrator. It involves using just two tools: the rectangle tool and the pen tool. Don’t worry if you don’t have much experience with the pen tool—we’re using it very simply. The method: draw a rectangle or square and then use the pen to delete a corner, instantly creating a right triangle.

These instructions will work in Adobe Illustrator from CS–CS5. The same strategy should work in any vector drawing program that allows you to use a pen-type tool to delete anchor points from a shape.

How to create a right triangle in Illustrator

1. Select the rectangle tool. (Keyboard shortcut m)
2. Use the rectangle tool to draw either a rectangle or square, depending on the type of right triangle you want.For a 45°-45°-90° triangle (half-square triangle) draw a square

   For all other right angles draw a rectangle

   A. Freehand method

   Square: Hold down the shift key on your keyboard, click and drag to draw a square of the desired size.
   Rectangle: Click and drag to draw a rectangle of the desired size.

   

   B. Exact-size method

   Click once anywhere on your artboard to open the rectangle dialog.

   

   Type in your desired dimensions for the legs of your triangle (not the hyptenuse).

   Click ok.

3. Select the pen tool. (Keyboard shortcut p)
4. Point your cursor in pen tool mode over the anchor (small square in shape outline) in one corner of your shape. The cursor will change into the delete anchor point tool.
   

   Click on that anchor to delete it.

5. Success. You should now have a right triangle.
   

If something happens so that your shape is deselected before you try to delete the anchor, use the select tool (black arrow tool, keyboard shortcut v), to click on your new shape so that it is selected, then try from step 3 again.