1. Composs point at angle vertex make an arc through both arms.
2. Compass point on vertex of 1st arc and one arm make another arc.
3.Repeat step 2 from another arm.
4. Draw a line from arc intersection to angle vertex.
How to make a perpendicular Bisector:
1. Open compss to just over half way of line segment
2.sharp part at point A make an arc.
3. Sharp part point B and make a arc.
4. With a ruler join the 2 intersections of the arcs.