Construct an equilateral triangle, by setting your compass to any length.
On one side of this, construct another equilateral triangle.
You now have 60° + 60° = 120°
How to construct angle 120?
2 answers
Or, since the sides of a regular hexagon are equal to the radius of the circle it is inscribed in, just
draw a circle
place the compass point on the circle, and with the same radius, draw an arc that cuts the circle in two places.
Joint those two points to the center of the circle.
The angle formed by those two lines is 120°
draw a circle
place the compass point on the circle, and with the same radius, draw an arc that cuts the circle in two places.
Joint those two points to the center of the circle.
The angle formed by those two lines is 120°