the.com/heptagon
the seven-sided shape too stubborn to tile a floor flat.
means A polygon with seven sides and seven angles.
from Pure Greek geometry: hepta, "seven," welded to gonia, "angle" or "corner" — literally "seven-cornered." That same -gon ending built the whole family, from pentagon to polygon, while hepta echoes in heptathlon and the week's seven days reimagined as a heptad.
- angle sum
- interior angles total exactly 900 degrees
- no tiling
- cannot tessellate a plane without gaps
- coin shape
- british 50p and 20p are heptagons
- construction
- impossible to draw with compass and straightedge
- name origin
- greek hepta, meaning seven
for instance
heptagonal british pound coin — uk currency introduced 1985, 7-sided for accessibility by visually impaired users
mel's hole — alleged heptagonal pit in ellensburg, washington, featured in paranormal legend