Content

• To step
• Method 1 of 2: Construct a bisector with a protractor
• Method 2 of 2: Constructing a bisector with a compass

You can cut a corner just like you can cut a line. To cut through means to divide something into two equal parts. There are two methods of dividing a corner in half. You can use the first method if you have a protractor, and if you need to find the degree measurement of the bisector. You can use the second method if you have a compass and ruler and only need to draw the bisector (without measuring it).

To step

Method 1 of 2: Construct a bisector with a protractor

1. Measure the angle. Place the caliper needle on the vertex of the corner, aligning the baseline with one of the corner's rays. Look at the degree mark where the other beam falls. This will give you the angle in degrees.
   • For example, the angle is 160 degrees.
   • Remember that a protractor has two sets of numbers. To know which set of numbers to use, consider the size of the angle. An obtuse angle is greater than 90 degrees and an acute angle less than 90 degrees.
2. Divide the number of degrees by two. The bisector of an angle divides it into two equal parts. So, to find where the angle bisector is, divide the number of degrees in the angle by two.
   • For example, if the angle is 160 degrees, you calculate ${ displaystyle { frac {160} {2}} = 80}$Draw a point to indicate the bisector. Align the point of origin with the vertex of the corner, and align the baseline with one of the rays. Find the center of the angle using the protractor. Mark this point on the inside of the corner.
     • For example, if the bisector of a 160 degree angle equals 80 degrees, find the 80 degree mark on the protractor and mark this point in the interior of the angle.
   • Draw a line from the vertex to the point. Use the straight part of the protractor to connect the vertex to the center of the angle. The line you draw is the angle bisector.

Method 2 of 2: Constructing a bisector with a compass

1. Draw an arc over both rays. Open the compass to any width and place the point of the compass on the vertex of the corner. Swing the compass so that the pencil draws an arc that crosses both rays of the corner.
   • Suppose you have an angle BAC. Place the compass tip on point A. Swing the compass so that it draws an arc that intersects radius AB at point D and radius AC at point E.
2. Draw an inner arc. Move the compass so that the point is where the first arc intersects the first ray. Turn the compass and draw an arc inside the corner.
   • For example, place the compass tip on point D and draw an arc inside the corner.
3. Draw a second inner arc that intersects the first inner arc. Without changing the width of the compass, move the point to where the first arc intersects the second ray. Turn the compass and draw an inner arc that intersects the first inner arc you drew.
   • For example, place the compass tip on point E and draw an arc that intersects the first inner arc. Label the point of their intersection F.
4. Draw a line from the vertex to the point where the arcs intersect. Use a ruler to make sure the line is accurate. This line cuts the corner in half.
   • For example, use a ruler to draw a line connecting points F and A.