The second scale along the top, which begins with zero on the left, meas-
ures angles that open in a clockwise arc. To measure a clockwise angle, place
the vertex in the circular opening at the base of the protractor and extend
the bottom ray through the 0° mark out to the left. In Figure 4.2, the
clockwise angle drawn is 120°:
How to Draw an Angle Using a Protractor
To draw an angle, first draw a ray. The ray’s end point becomes the angle’s
vertex. Position the protractor as if you were measuring an angle. Choose
your scale and make a mark on the page at the desired measurement.
Remove the protractor and connect the mark you made to the vertex with
a straight edge. Voilà, you have an angle.
0 180 0 1806060 ̊120Figure 4.2501 Geometry Questions