How to Make a 45 Degree Angle Without a Compass

Written by david robinson
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How to Make a 45 Degree Angle Without a Compass
Protractors are accurate and inexpensive tools for drawing angles. (George Doyle/Stockbyte/Getty Images)

Drawing angles is a skill required in many situations, from school lessons through to working as a cartographer or rocket engineer. Although it is possible to draw many angles with a compass, it is not the only tool available. A semicircular protractor is a useful tool for measuring and drawing angles not exceeding 180 degrees. A protractor has an outer edge marked in degrees, from zero to 180, and a horizontal baseline and vertical centerline to facilitate accurate positioning. Using a protractor is simple.

Skill level:

Things you need

  • Protractor
  • Pencil

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  1. 1

    Draw a horizontal line using the flat base of the protractor. Draw a short vertical line crossing the horizontal one near the left-hand end of the line. This provides a guide for positioning the protractor in Step 2.

  2. 2

    Rest the protractor over the horizontal line. Ensure that the protractor baseline -- joining zero degrees and 180 degrees -- is exactly on top of the line, and that the vertical line in the centre of the protractor base aligns with the vertical guideline drawn in Step 1.

  3. 3

    Locate the 45-degree mark on the curved perimeter of the protractor and make a small pencil mark on the drawing surface.

  4. 4

    Move the protractor and use the straight base to draw a line between the guide mark on the horizontal line and the mark representing 45 degrees. The angle between the two lines is 45 degrees.

Tips and warnings

  • Use a semicircular protractor to measure any angle between zero and 180 degrees.
  • Full circle protractors enable any angle to be drawn.
  • Some drafting triangles have 45-degree corners.
  • Blunt and wide-tipped pencils reduce the accuracy of measurements. Always use a sharp pencil.

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