90 (number)

The rhombic enneacontahedron is a zonohedron with a total of 90 rhombic faces: 60 broad rhombi akin to those in the rhombic dodecahedron with diagonals in ${\displaystyle 1:{\sqrt {2}}}$ ratio, and another 30 slim rhombi with diagonals in ${\displaystyle 1:\varphi ^{2}}$

: ${\displaystyle 109.471}$°. It is the dual polyhedron to the

simple polyhedron

.

The truncated dodecahedron and truncated icosahedron both have 90 edges. A further four uniform star polyhedra (U₃₇, U₅₅, U₅₈, U₆₆) and four uniform compound polyhedra (UC₃₂, UC₃₄, UC₃₆, UC₅₅) contain 90 edges or vertices.

The

${\displaystyle _{3}\{4\}_{3}}$

arrangement of the ${\displaystyle 4_{21}}$

${\displaystyle \left[{\begin{smallmatrix}40&9&12\\4&90&4\\12&9&40\end{smallmatrix}}\right]}$ or ${\displaystyle \left[{\begin{smallmatrix}40&12&12\\2&240&2\\12&12&40\end{smallmatrix}}\right].}$

This Witting configuration when reflected under the

${\displaystyle \operatorname {PG} {(3,2^{2})}}$

${\displaystyle 85=45+40}$

${\displaystyle 27+90+240=357}$

Whereas the rhombic enneacontahedron is the

${\displaystyle \mathrm {E} _{8}}$

In science

Ninety is:

• the atomic number of thorium, an actinide. As an atomic weight, 90 identifies an isotope of strontium, a by-product of nuclear reactions including fallout. It contaminates milk.
• the latitude in degrees of the North and the South geographical poles.

In sports

• goalkeeper gloves
• bases
  are 90 feet (27 m) apart.
• The car number most associated with former NASCAR team owner Junie Donlavey
• The total number of minutes in an association football match.

In other fields

• +90 is the
  code for international direct dial phone calls to Turkey
  .
• 90 is the code for the French département Belfort.
• controlled access highway that spans the continental United States for 3,020 miles (4,860 kilometers) from Seattle to Boston
  .

References