Answer
Use a compass, adjust the gap of the two leg tips to be equal to the radius, fix the tip of one leg at the center and rotate the other leg with an attached pencil to draw the circle.
Work Step by Step
Based on the definition of a circle, use a compass, adjust the gap of the two leg tips to be equal to the radius, fix the tip of one leg at the center and rotate the other leg with an attached pencil to draw the circle.