How to construct a pentagon

Hi there,
to make a pentagon is a piece of cake after reading this post.
You will need a degree ruler (don't know if that's the correct word but look at the pictures)a compass, pen and paper.
It's a big calculation (at least it is to me)to find the radius in a circle wich will give us a pentagon with sides measuring 3 cm.
My darling husband did this job for me, and the radius must be 2.55 cm.(US 1 inch)
Make a circle that big. Use the ruler and mark 90 deg. from mid point. Then mark 36 deg. to each side of the 90 deg. mark on top.
Take your compass and fit it in between the 2-36 deg. marks. Mark this distance a further 3 times at your circle. Draw straight lines through all marks and VOILA you have your pentagon with 3cm sides.
Look at your figure and imagine a house, you could easily lengthen the "walls" skip the lid and you have made yourself a unik vase.
I will write down the calculation formula wich gives the radius of a circle when side length is given in forehand, for those of you who can manage such kind of magic.
R = side lenght / 2 x sin36 deg. (This is Greek to me. :-)
I believe you all can make a hexagon so I don't mention that. If not ask me.
ENJOY!!!