Example Solution: Since protractors have the scale for both acute and obtuse angles along the top, the supplement is the measure of the given angle on the other scale.
Practice makes perfect
To measure an angle, we can use a protractor. We always place the center point of the protractor on the vertex of the angle.
Notice that the largest angle that a protractor can measure is 180. Let's measure any angle.
We can tell that ∠ 1 and ∠ 2 are supplementary angles.
m ∠ 1+ m ∠ 2 = 180
As we can see, protractors have the scale for both acute and obtuse angles along the top. If we want to read the measure of ∠ 1, we use the inner scale. However, we can also read the measure on the outer scale. This is the measure of ∠ 2, which is the supplement of ∠ 1.
