Forget the diameter.
Find the centre.
Draw any radius.
Next, add another radius at 360/9 = 40 degrees to the first.
Keep adding radii as you go around the circle. When it is in 9 equal slices you will have returned to the first radius.
Done.
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The circumference of a circle divided by its diameter is equal to the value of pi
Only the diameter can divide the circle in to two equal parts.
well the circumference is equal to pi times the diameter, so all that you have to do is divide the circumference by pi to get the diameter. Then you divide the diameter by two to get the radius.
Since Pi is equal to the circumference over diameter, the diameter of a circle is equal to its circumference over Pi. So divide 24 centimeters by 3.14159 to get approximately 7.63943 centimeters.
The diameter is equal to half of the radius. So take the value of the diameter and divide it by two and that is your radius.