### artwork | illustration | figure:

Quaternion
* are a compact way of representing rotations
  - mathematical oddity
  - convenient alternatives to Matrices for storing rotations
* have rules for addition and multiplication
  - the same continuum properties as the real and complex numbers
  - three imaginary axes, which creates the factor of three

Regular polygon
* are both equiangular and equilateral
  - ones in which the sides have the same length and the angles are all equal
* have both rotational and reflectional symmetry
  - n sides, all the same length

### artwork | illustration | figure | regular polygon:

Equiangular triangle
* All equiangular triangles are congruent to all equilateral triangles.
* regular polygon
  - whose three angles are congruent

Equilateral triangle
* All equilateral triangles have the same shape.
* Every equilateral triangle is isosceles.
* are regular polygons
  - triangles whose sides are all the same length
* symbolize the godhead, harmony and proportion.

Sector
* Many sectors do rise and fall according to business or economic cycles.
* are aspects.
* are part of battlefields
  - blocks
  - economy
  - societies
  - social groups
  - the wedge-shaped divisions of the disk
  - tracts
* investing concentrates investment dollars in one group of related companies.

### artwork | illustration | figure | sector:

Economic sector
* consume different amounts of different types of floor-space.
* employs people to produce goods and services.
* have to change and carry their part of the responsibility for sustainability.

Private sector
* are much higher paying than government or nonprofit sectors
  - responsible for delivery of high quality equipment to satisfy individual needs
* is seen as the partner in economic development in Iowa rather than government.
* is the commercial sector while People sector aims at community services
  - primary engine of economic growth
* plays important role in reducing production costs, competing on world markets.

Tertiary sector
* is the provision of services.
+ Economic sector, Based on place in the production chain: Economics
  * Primary sector extracts natural materials and provides raw materials for secondary industry. Secondary sector processes raw materials or semi-finished goods into more valuable products. Tertiary sector is the provision of services. Quaternary sector is the activity related to the application, manipulation and transmission of information.

Semicircle
* Any semicircle passing through the poles is called a meridian of longitude.
* are arcs.

Significant digit
* are digits
  - the first digit before the decimal point, and all the digits after it
* determine the precision of the numbers used in calculations.
* is one way of keeping track of how much error there is in a measurement.

Significant figure
* Significant Figures play an important part in scientific measurement.
* is the number of digits excluding leading and trailing zeros.

Tetrad
* come in seven shapes.
* move to metaphase plate.

Trapezoid
* All trapezoids are quadrilaterals.
* Every trapezoid parallelogram.
* are figures
  - special parallelograms
* have exactly one pair of opposite sides that are parallel.

Tree diagram
* are often useful in connection with conditional probabilities
  - useful because they can disambiguate ambiguous sentences
* depict patterns.

Trine
* are video games.
* reduce stress, friction and discomfort.

Trio
* are ensembles
  - gathering
  - musical compositions
  - sets
+ Trio (music)
  * Trios can also apply to popular music, like Nickel Creek.

### asbestos:

Chrysotile
* is asbestos
  - much less ecopersistent than other types of asbestos
* occurs chiefly in association with massive serpentine.