PROTRACTORInstrument used for measuring
and laying off angles.
PYRAMIDA figure having a plane polygon for
its base and triangles meeting at a common vertex
for its sides.
PYTHAGOREAN THEOREMA law of
mathematics that states that the square of the
hypotenuse of a right triangle equals the sum of
the squares of the other two sides.
QUADRILATERALA polygon bounded by
QUALITATIVE CHART OR GRAPHAny
chart that emphasizes the relationships of facts.
QUANTITATIVE CHART OR GRAPHA
chart or graph that emphasizes numerical values.
RADIANA system for measuring angles where
2n radians equals 360°; 1 radian = 57.3°.
RADICALA symbol placed on a mathematical
quantity to indicate the root of the quantity; for
RADIUS-A straight line from the center of a
circle or sphere to its circumference or surface.
RATIO-A comparison of two like quantities; for
example, 2/3, 2:3.
RATIONAL NUMBERA number that can be
expressed as the quotient or ratio of two whole
numbers: Fractions 2/7, Integers 3/1 = 3. A
radical is a rational number if the radical is
removable; for example, ~ = 2, @ = 3.
REAL NUMBERSAll positive and negative
RECIPROCALThe reciprocal of
equals 1 divided by the number.
adjacent sides join at right angles.
RECTANGULAR PRISMA solid figure whose
base is a rectangle.
REFERENCE PLANEThe normal plane from
which all information is referenced.
REGULAR POLYGONAn equilateral polygon.
RESIDUAL SOILAny soil that results from
weathering in place and that is not moved from
its place of origin.
RETICLEA system of wires, hairs, threads,
etched lines, or the like, placed normal to the axis
of a telescope at its principal focus by means of
which the telescope is sighted on a star, or target,
or by means of which appropriate readings are made
on some scale, such as a leveling or stadia rod.
REVERSE CURVESee OGEE CURVE.
REVISION BLOCKBlock drawn in the upper
right corner of construction drawings; contains
chronological list of all changes or revisions to
REVOLUTIONObject is projected on one or
more of the planes of projection but rather than
being in the normal position, it is revolved on an
axis perpendicular to one of the regular planes;
used when it can show the features of an object
more clearly than a normal orthographic projection.
REVOLVED SECTIONA sectional view used
to show the internal structure of an item within
the normal orthographic view.
RHOMBOIDA nonequilateral parallelogram in
which adjacent sides join at oblique angles.
RHOMBUSAn equilateral parallelogram in
which adjacent sides join at oblique (other than
RIGHT ANGLEAn angle of 90°.
ROOTThe number of times a quantity is found
as an equal factor within another quantity; for
$%= 4th root of 16 = 2