A protractor is used not only for measuring but also for constructing or drawing angles. The following examples illustrate how you can draw an angle if the measure of the angle is given.

Example

Draw an angle of 40° using a protractor
Solution
Steps:

• Draw a baseline AB.
• Mark the point O and place the center of the protractor at O.
• Align the baseline of the protractor with the line OB.
• In the inner readings, look for 40^o and mark it as point C.
• Now using a ruler, join O and C.
• m∠COB = 40°

Remember, if you take ray OA as your base line and align the protractor with it, you start reading from the outer 0⁰ on the left and mark D at 40⁰. Joining O and D, you will have m∠DOA = 40°.