Bisecting Angles - JSS2 Mathematics Lesson Note

Using a Compass and a Ruler

Steps:

Draw the Angle:

Draw an angle ∠𝐴𝐵𝐶 with vertex 𝐵.

Arc Intersection:

Place the compass at the vertex 𝐵 and draw an arc that intersects both arms of the angle. 

Label the intersection points as 𝐷 and 𝐸.

Intersecting Arcs:

Without changing the compass width, place the compass at 𝐷 and draw an arc inside the angle.

Repeat the process by placing the compass at 𝐸 and draw another arc that intersects the first arc. Label the intersection point as 𝐹.

Draw the Bisector:

Draw a lie from the vertex 𝐵 through the intersection point 𝐹. This line bisects the angle ∠𝐴𝐵𝐶 into two equal parts.

Example: Bisect an angle ∠𝐴𝐵𝐶.

Steps:

Draw ∠𝐴𝐵𝐶.

Place the compass at 𝐵 and draw an arc intersecting 𝐴𝐵 and 𝐵𝐶 at 𝐷 and 𝐸.

With the same compass width, draw arcs from 𝐷 and 𝐸 that intersect at 𝐹.

Draw line 𝐵𝐹 to bisect ∠𝐴𝐵𝐶.