1) Construct 60°
- Draw an arc on the line segment.
- From that arc, from the point where it intersects the line draw one more arc of the same radius so that it intersects the first arc. You got 60°
2) Draw 120°
- From the point where the arc intersects 60°, draw one more arc of the same radius. Extend the first arc to that arc. You got 120°.
3) Bisect the angle between 60° and 120°
- You get 90°
4) Bisect the angle between 90° and 120°.
- You get 105°.