Geometry: using only compasses and straightedge
Make a dot and draw a circle round it.
Draw perpendiculars (diameters) through the central dot. (How to draw perpendiculars?)
Draw a point half way between the centre and one side of a diameter.
Join that point to the top.
Centre your compasses at C and draw a circle with radius CB to cut the diameter at D.
Divide AD in half at E. (How?) OK be lazy, use a ruler.
Divide AD in half at E. (How?) OK be lazy, use a ruler.
Draw a perpendicular through E to meet the circle at F anf G. The two purple lines FH and HG are two sides of a pentogram.
Use your compasses set at width FH to make the three remaining sides.
How to draw a regular pentogram.