T - Math terms glossary

table  An arrangement of data in rows and columns.

Take-away Model for Subtraction If a quantity y is taken away from an original quantity x with the same units, the quantity left is x - y.

tangent A line, ray, segment, or plane which intersects a curve or curved surface in exactly one point.

tangent of an angle The ratio (length of leg opposite to the angle/length of leg adjacent to the angle) in a right triangle. Abbreviated tan.

tangent circles Two circles that have exactly one point in common.

EX: Here we see a design made of lots of tangent circles.

tenth  A word name for

terminal point The endpoint of a vector.

terminating decimal  A decimal that ends. Also called finite decimal.

terms  Numbers or products of numbers and variables that are added.

Ex: 3x +-8xy + 9 is an expression with three terms.
Ex: also has three terms, remember the last subtraction here can be written as + .

tessellation  A filling up of a two-dimensional space by congruent copies of a figure that do not overlap. The figure which is copied is commonly called the "fundamental region"

tetrahedron A polyhedron with four faces.

theorem A statement deduced from postulates, definitions, or other previously deduced theorems.

30-60-90 triangle A triangle in which the three angles measure 30, 60, and 90.

3-dimensional coordinate system A system of coordinates used to locate points in space by their distances and directions from three mutually perpendicular lines.

three-dimensional figure A figure whose points do not all lie in a single plane.

transformation  The movement of a figure in a plane from its original position, the preimage, to a new position, the image. Also called a map. Transformations can occur when there is a reflection, a rotation, a translation, or a glide reflection of the original image.

translation A transformation in which every point of the preimage moves in the same direction by the same amount to form the image. A translation is also referred to as a "slide".

translation image The result of adding the same numbers to the coordinates of the points in a figure. In the drawing above, triangle A'B'C' is the translation image of triangle ABC. Also called slide image.

transversal A line that intersects two or more lines.

trapezoid A quadrilateral that has (at least) one pair of parallel sides.

*NOTE some definitions omit the words at least.

traversable network A network in which all the arcs may be traced exactly once without picking up the tracing instrument.

*NOTE: a network is only traversable if it has less than three odd nodes (an odd node has an odd number of arcs entering it).

trial and error  A problem-solving strategy in which various solutions are tried until the correct solution is found.

triangle A polygon with three sides.

Triangle-Sum Property  In any triangle, the sum of the measures of the angles is 180°.

triangular region  A triangle and the space inside it.

triangulate To split a polygon into nonoverlapping triangles. Triangulation is usually used to help find the areas of polygons.

trigonometric ratio A ratio of the lengths of the sides in a right triangle.

trillion  A word name for 1,000,000,000,000 .

trillionth A word name for , or .00000 00000 01.

trisect To divide into three congruent parts.

truncate  To cut off a number at a particular decimal place. Truncation does not mean that the decimal is rounded up, a part of it is simply cut off.

Ex: 0.666666666666666 truncated to the hundredths place is 0.66.
*NOTE some calculators are programmed to truncate and others to round up. A rounding calculator with a ten digit display would show 0.666666667 for the decimal above.

truth value The condition of a statement in logic; either true or false.

turn A transformation in which every point of the preimage is rotated by a given angle about a point (in two dimensions) or a line (in three dimensions).They are also called rotations.

A turn in the clockwise direction is considered negative and one in the counterclockwise direction is considered positive.

two-column proof A form of written proof in which the conclusions are written in one column and the justifications are written beside them in a second column.

EX:

Given: Figure ABCDEF as drawn below
Prove: Figure ABCDEF is not a polygon.
1.) Figure ABCDEF is a union of segments in the plane:	1.) Given
2.) , , , , and are the only segments in the figure.	2.) Given
3.) intersects with only at point B, and point A intersects no other segment.	3.) Given
4.) Therefore, Figure ABCDEF is not a polygon.	4.) It violates the definition of polygon.

two-dimensional Pertaining to figures that lie in a single plane, or to their geometry. This is "flat land" so to speak.