compass

To inscribe a regular hexagon in a circle.
Given:  Circle with center O.
Required:  To inscribe a hexagon in circle O.
Procedure:

inscribe a hexagon in a circle

  Label any point on the circle point A.
  Use the segment command under the construct menu and construct segment OA.
  Use the circle by center + radius command under the construct menu and construct a circle with center A and radius congruent to segment OA.
  Moving counterclockwise around the original circle O, label the point of intersection of these two circles B.
  Repeat the above steps around the circle, until you have 6 points labeled.
  Use the segment command under the construct menu and construct segments AB, BC, CD, DE, EF, and FA.
  Hexagon ABCDEF is the required hexagon.
Proof:
  OA = OB = AB  ( radii of equal circles are equal) 
  OAB is equilateral and   equiangular.  (An equilateral is equiangular)              
    AOB = 60 arc CD = 60 or 1/6 of a circle. (A central measure = its intercepted arc and there are 360 in a circle.) 
  Chord AB is a side of a regular hexagon.  Likewise for the rest of the chords. ABCDEF is a regular hexagon.
Sketch:   Before you try to move the points on the sketch below, can you predict which ones will move so that you can change the size of the hexagon?
 
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inscribe a regular hexagon in a circle

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