R

**R: abbreviation for the real numbers.**

**radian: the ratio of an arc of a circle to the radius
of the circle. On a unit circle, a full **

** rotation
around the circle is 2 pi radians. On any circle, a full
rotation is 2pi r **

** radians.**

**radius: the distance from the center to a point
on a circle. The line segment from the **

** center
to a point on a circle.**

**range: the set of all possible values for the output
of a function.**

**ratio: the ratio of two real numbers, a and
b, is a/b.**

**rational number: a number that can be expressed as the
ratio of two integers.**

**real numbers: the union of the set of rational numbers
and irrational numbers.**

**reciprocal: the reciprocal of a number, a,
is 1/a, (a cannot be zero).**

**rectangle: a quadrilateral with four 90 degree angles.**

**rectangular coordinates: same as Cartesian Coordinates.**

**reflection: mirror image.**

**reflexive property: x = x for all
x. Every number equals itself.**

**regular polygon: a polygon in which all the angles are
equal and all of the sides are equal.**

**regular polyhedron: a polyhedron whose faces are
congruent, regular polygons.**

**relation: a set of ordered pairs.**

**remainder: if m = nq + r, then m/q
has quotient q and remainder r.**

**repeating decimal: a decimal in which the digits endlessly
repeat a pattern.**

**rhombus: a quadrilateral with four equal sides.**

**right angle: an angle whose measure is 90 degrees.**

**right circular cone: a cone whose base is a circle located
so that the line connecting the **

** vertex
to the center of the circle is perpendicular to the plane **

** containing
the circle.**

**right circular cylinder: a cylinder whose bases are circles
and whose axis is perpendicular **

** to
its bases.**

**right triangle: a triangle that contains a right angle.**

**root: the root of an equation is the same as the solution
to the equation.**

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