54 Diagonals and 10 different triangles made from diagonals
Real Life Examples
In block capitals, the letters H, X and E(and I in a slab serif font) have dodecagonal outlines.
The regular dodecagon features prominently in many buildings. The Torre del Oro is a dodecagonal military watchtower in Seville, southern Spain, built by the Almohad dynasty. The early thirteenth century Vera Cruz church in Segovia, Spain is dodecagonal. Another example is the Porta di Venere (Venus' Gate), in Spello, Italy, built in the 1st century BC has two dodecagonal towers, called "Propertius' Towers".
Regular dodecagonal coins include:
British threepenny bit from 1937 to 1971, when it ceased to be legal tender.
British One Pound Coin to be introduced in 2017.
Australian 50-cent coin
Fijian 50 cents
Tongan 50-seniti, since 1974
Solomon Islands 50 cents
Croatian 25 kuna
Romanian 5000 lei, 2001–2005
Canadian penny, 1982–1996
South Vietnamese 25 đồng, 1968–1975
Zambian 50 ngwee, 1969–1992
Malawian 50 tambala, 1986–1995
Mexican 20 centavos, since 1992
Teselation
Four Examples
Construction
Use a compass to draw a circle
Draw a pair of perpendicular lines that meet at the center of the circle. One horizontal and one verticle.
Make two circle that center at the two spots where the verticle line intersects the circle. The curve of the two circles have to meet at the center of the original circle.
Make two circle that center at the two spots where the horizontal line intersects the circle. The curve of the two circles have to meet at the center of the circle you made in step one.
Starting at the top of the circle, where the verticle line meets the curve, draw a line from there to the nearest point where the large circle's curve intersects with a line or another curve.
Draw another line from there to the the next intersection along the curve and keep on doing that in a clockwise(or counter-clockwise) direction.
Erase all lines and curves except the ones made in the past 2 steps.
Graphing
If a regular dodecagram with each side having 2 units long was graphed with the center at (0,0), the coordinate would be: