Mathematics uses many concepts in threes. The first structure mathematically is a triangle. There are acute, right, and obtuse angles. Trigonometry is the study of the relationship of the sides of a triangle. Have your heard of Pascal's Triangle?
This rule applies generally to a variable X having normal (bell-shaped or mound-shaped) distribution with mean "mu" (the greek letter) and standard deviation "sigma" (the greek letter). However, this rule does not apply to distributions that are not normal.
Pythagoras calls three the perfect number, expressive of “beginning, middle, and end,” wherefore he makes it a symbol of Deity. The world was supposed to be under the rule of three gods, viz. Jupiter (heaven), Neptune (sea), and Pluto (Hades).
These pointers discuss triangles and their higher-dimensional generalizations (simplices). I am particularly interested in triangulation by which I mean partitioning regions into triangles, tetrahedra, or higher dimensional simplices, for various applications including finite element mesh generation and surface interpolation. (The other meaning of triangulation involves determining locations and distances from certain measurements.) For more material on the first type of triangulation, see the mesh generation section of Geometry in Action or the list of my own triangulation papers. For other kinds of partitions, see the page on dissection.
The “Flower of Life” can be found in all major religions of the world. It contains the patterns of creation as they emerged from the “Great Void”. Everything is made from the Creator’s thought. After the creation of the Seed of Life the same vortex’s motion was continued, creating the next structure known as the Egg of Life.
What percentage of all integers contains at least one instance of the digit three? For example, 13, 31, 33 and 103 all contain the digit "three" at least once. ANSWER! Answer: How Many Threes? 100% of all integers contain at least one three. What?!? How can this be? The solution is so surprising, it is difficult, if not impossible to believe that 100% of integers contain the digit three at least once.
In set theory, a relation that is reflexive, symmetric, & transitive on a set X is called an equivalence relation on X. SImply put as a graph, reflexive me ans there is a loop, symetric means for every directed edge from v to w, there is also a directed edge from w to v, and transitive means for a directed edge x to y, and y to z, there is also an edge from x to z.