If you measure the radius, then start from a point on the circumference, and set off a chord (a straight line that touches the circumference at both ends, equal to the radius, and from the end of that chord set off another one, the end of the second chord will be on a point 1/3 of the circumference.
Old guy
How about measuring the circumference, dividing by 3 and marking the circumference by the result. Draw a line to the center from those 3 points.
How do you propose to measure the circumference?
Wrap a string around it, measure the string.
Fabric tape measure.
carpenter's
rotating that
method of
easier?
Get yourself a shashigane (Japanese Carpenter's Square) marked in the shaku/sun system and learn to use it. Unlike American style framing squares, they are marked on the back side for folks that work with logs (circles). They are very handy for marking squares, and other geometric shapes, on the end of a log, or inside a circle, without a lot of fuss.
Len
Dunno how a four sided figure would help, but here's a way to inscribe an equilateral triangle using a steel square:
Use bisection to bisect the circle with a line, then bisect the 1st line at a right angle. Draw lines from the points where the two lines intersect the circle (4 pts). Voila! Square in circle.
Now that you have the square, do you have a solution for the problem, dividing the circle into 3 equal pie sections?
Leon, Thanks, I was about to ask notbob that same thing. Kerry
Ask the boatbuilder.
I was jes showing an easy way to make a square inside a circle. For the three angles in a circle, I'd use a hexagon.
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