• APPLICATION IN DAILY LIFE

•By Karthik, Krishna, Magesh, Makesh and Ram ananth

•In geometry, a tetrahedron is a polyhedron composed of four triangular 0f faces, three of which meet at each vertex. It has six edges and four vertices. The tetrahedron is the only convex polyhedron that has four faces. •The tetrahedron is the three-dimensional case of the more general concept of a Euclidean simplex. •The tetrahedron is one kind of pyramid, which is a polyhedron with a flat polygon base and triangular faces connecting the base to a common point. In the case of a tetrahedron the base is a triangle (any of the four faces can be considered the base), so a tetrahedron is also known as a "triangular pyramid".

•The shape, tetrahedron, has a variety of applications ranging from chemistry to sports. •The uses of tetrahedron can be widely classified into •Chemistry •Electrical and electronics •Games •Contemporary Art

•Alexander Graham Bell was a proponent of use of the tetrahedron in framework structures, including kites .The opposite edges of a regular tetrahedron are perpendicular, and so can form a universal coupling if hinged appropriately. •Eight regular tetrahedra can be placed in a ring which rotates freely, and the number can be reduced to six for squashed irregular tetrahedra .

•The tetrahedron shape is seen in nature in covalent bonds of molecules. All sp3-hybridized atoms are surrounded by atoms lying in each corner of a tetrahedron. •For instance in a methane molecule (CH4) or an ammonium ion (NH4

+), four hydrogen atoms surround a central carbon or nitrogen atom with tetrahedral symmetry. •For this reason, one of the leading journals in organic chemistry is called Tetrahedron.

•The central angle between any two vertices of a perfect tetrahedron is , or approximately 109.47

. •Water, H2O, also has a tetrahedral structure, with two hydrogen atoms and two lone pairs of electrons around the central oxygen atoms. •Its tetrahedral symmetry is not perfect, however, because the lone pairs repel more than the single O-H bonds.

•If six equal resistors are soldered together to form a tetrahedron, then the resistance measured between any two vertices is half that of one resistor. •Since silicon is the most common semiconductor used in solid-state electronics, and silicon has a valence of four, the tetrahedral shape of the four chemical bonds in silicon is a strong influence on how crystals of silicon form and what shapes they assume.

•Especially in roleplaying, this solid is known as a 4-sided die, one of the more common polyhedral dice, with the number rolled appearing around the bottom or on the top vertex. Some Rubik's Cube-like puzzles are tetrahedral, such as the Pyraminx and Pyramorphix. •The net of a tetrahedron also makes the famous Triforce from Nintendo's The Legend of Zelda franchise.

•The Austrian artist Martina Schettina created a tetrahedron using fluorescent lamps. It was shown at the light art biennale Austria 2010. •It is used as album artwork, surrounded by black flames on The End of All Things to Come by Mudvayne.

•A colour model is an abstract mathematical model describing the way colours can be represented as tuples of numbers, typically as three or four values or colour components (e.g. RGB and CMYK are colour models). •Tetrahedra are used in colour space conversion algorithms specifically for cases in which the luminance axis diagonally segments the colour space (e.g. RGB, CMY).

•The tetrahedral hypothesis, originally published by William Lowthian Green to explain the formation of the Earth, was popular through the early 20th century. •It was still popular in 1917 when summarized as: •"The law of least action … demands that the somewhat rigid crustal portion of the earth keep in contact with the lessening interior with the least possible readjustment of its surface. … a shrinking sphere tends by the law of least action to collapse into a tetrahedron, or a tetra-hedroid, a sphere marked by four equal and equidistant triangular projections; and the earth with its three about equal and equidistant double continental masses triangular southward with three intervening depressed oceans triangular northward, its northern ocean and southern continent, with land everywhere antipodal to water, realizes the tetrahedroid status remarkably.“ •This is suggesting that a cooling spherical Earth might have shrunk to form a tetrahedron, with its vertices and edges forming the continents, and four oceans (Pacific Ocean, Atlantic Ocean, Indian Ocean and Arctic Ocean) on its faces.