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