Equilateral triangle a triangle with any two sides "a" and "b", and an angle "C" between them is Each angle of an equilateral triangle is 60°, so The sine of 60° is formula_50. Thus since all sides of an equilateral triangle are equal. Equilateral triangles have frequently appeared in man made constructions: Equilateral triangle In geometry, an equilateral triangle is a triangle in which all three sides are equal. In the familiar Euclidean geometry, an equilateral triangle is also equiangular; that is, all three internal angles are also congruent to each other and are each 60°. It is also a regular polygon,
Sierpinski triangle the Sierpinski triangle. The Sierpinski triangle may be constructed from an equilateral triangle by repeated removal of triangular subsets: Each removed triangle (a "trema") is topologically an open set. This process of recursively removing triangles is an example of a finite subdivision rule. The same sequence of shapes, converging to the Sierpinski triangle, can alternatively be generated by the following steps: Note that this infinite process is not dependent upon the starting shape being a triangle—it is just clearer that way. The first few steps starting, for example, from a square also tend towards a Sierpinski triangle. Michael Barnsley used