Equilateral triangle
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An equilateral triangle is a triangle in which all three sides have the same length, and all three angles are equal. Because of these properties, the equilateral triangle is a regular polygon, occasio
The regular octahedron is a deltahedron, as well as a member of the family of antiprisms.
Equilateral triangle usage as a yield sign
Angle trisection
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Angle trisection is the construction of an angle equal to one third of a given arbitrary angle, using only two tools: an unmarked straightedge and a compass. It is a classical problem of straightedge
Rulers. The displayed ones are marked — an ideal straightedge is un-marked
Compasses