SOLUTION: A,regular octagon of side 6cm is inscribed in acircle.calculate the diameter of the circle

1.  Make a sketch.

    Draw the apothem in the regular octagon.

2.  The central angle is  =  = 45 degs.

    The acute angle in the right-angled triangle is  =  = 22.5 degrees.


    From the right-angled triangle, you have  = ,   or

    R = .


    You can find  using your calculator or using the formula

     = .