Radical form
Radicand See
Radical form.
Radius The distance
of a point on a circle from the center of the same circle.
RAM Random-Access
Memory, or memory where each location is uniformly accessible,
often used for the storage of a program and the data being
processed.
Random Variable
A random variable X is associated with the sample
space S of a probability is a function that assigns
a real number to each simple event in S .
Range In statistics,
it is the difference between the largest and the smallest
numbers in the data set.
Rate (1) In percent
problems, it is the percent. (2) In tax problems, it is
the level of taxation, written as a percent. (3) In financial
problems, it refers to the APR.
Ratio The quotient
of two numbers or expressions.
Rational equation
An equation that has at least one variable in the
denominator.
Rational number
A number belonging to the set Q defined by
Q = {a/b such that a is an integer and b
is a nonzero integer}
a is called the numerator and b is
called the denominator. A rational number is
also called a fraction.
Ray If P is
a point on a line, then a ray from the point P is all points
on the line on one side of P .
Real number
line A line on which points are associated with
real numbers in a one-to-one fashion.
Real numbers
The set of all rational and irrational numbers, denoted
by R.
Reciprocal The reciprocal
of n is 1/n, also called the multiplicative inverse of n.
Rectangle A
quadrilateral whose angles are all right angles.
Rectangular
coordinate system See Cartesian coordinate system.
Rectangular
coordinates See Ordered pair.
Rectangular
parallelepiped In this book, it refers to a box
all of whose angles are right angles.
Reduced fraction
A fraction so that the numerator and denominator have no
common divisors (other than 1).
Reducing fractions
The process by which we make sure that there are no common
factors (other than 1) for the numerator and denominator
of a fraction.
Reflection
Given a line L and a point P, we call the
point P' the reflection about the line L if
the line segment connecting P and P' is perpendicular
to L and is also bisected by L.
Region In a network, a separate
part of the plane.
Regression
analysis The analysis used to determine the relationship
or a correlation between two variables.
Relation A
set of ordered pairs.
Relative frequency
If an experiment is repeated n times and an event occurs
m times, then the relative frequency is the ratio m/n.
Relatively prime
Two integers are relatively prime if they have no common
factors other than 1, -1; two polynomials are relatively
prime if they have no common factors except constants.
Remainder
When an integer M is divided by a positive integer
n, and a quotient q is obtained for which
M = nq + r with 0 <= r < n,
then r is the remainder.
Repeating decimal
See Decimal fraction.
Repetitive
system
A property of a numeration system for which a single
symbol is repeated to represent a given number.
Replication
On a spreadsheet, the operation of copying a formula from
one place to another.
Resolution
The number of dots (or pixels) determines the clarity, or
resolution, of the image on the monitor.
Revolving credit
It is the same as open-end or credit card credit.
Rhombus A parallelogram
with adjacent sides equal.
Richter number
A number used to denote the magnitude or size of an earthquake.
Richter scale
Same as Richter number.
Right angle
An angle of 90Î.
Right circular cone A
cone with a circular base for which the base is perpendicular
to its axis.
Right
circular cylinder A cylinder with a circular base
for which the base is perpendicular to its axis.
Right prism
A prism whose base is perpendicular to the lateral edges.
Right triangle
A triangle with one right angle.
Rise See Slope.
ROM Read-Only Memory,
or memory that cannot be altered either by the user or a
loss of power. In microcomputers, the ROM usually contains
the operating system and system programs.
Root of a number
An nth root (n is a natural number) of a number
b is a only if an = b.
If n = 2, then the root is called a square root;
if n = 3, it is called a cube root.
Root of an equation See
Solution.
Roster Method
A method of defining a set by listing its members.
Rounding a
number Dropping decimals after a certain significant
place. The procedure for rounding is:
1. Locate the rounding place digit;
2. Determine the rounding place digit: It stays the same
if the first digit to its right is a 0, 1,
2, 3, or 4; it increases by 1 if the
digit to the right is a 5, 6, 7, 8, or 9.
3. Change digits: all digits to the left of the rounding
digit remain the same (unless there is
a carry) and all digits to the right
of the rounding digit are changed to zeros.
4. Drop zeros: If the rounding place digit is to the left
of the decimal point, drop all
trailing zeros; if the rounding
place digit is to the right of the decimal point, drop all
trailing zeros to the right of the rounding
place digit.
Row A horizontal
arrangement of numbers or entries of a matrix. It is denoted
by numerals 1, 2, 3, ... on a spreadsheet.
Row+ An elementary
row transformation that causes one row of a matrix (called
the pivot row) to be added to another row (called the target
row). The answer to this addition replaces the entries in
the target row, entry-by-entry.
Row-reduced
form The final matrix after the process of Gauss-Jordan
elimination.
RowSwap An elementary
row operation that causes two rows of a matrix to be switched,
entry-by-entry.
Rubik's cube
A three-dimensional cube that can rotate about all three
axes. It is a puzzle that has the object of returning the
faces to a single color position.
Rules of
divisibility A number N is divisible by:
1
2 if the last digit is divisible by 2.
3 if the sum of the digits is divisible by 3.
4 if the number formed by the last two digits is divisible
by 4.
5 if the last digit is 0 or 5.
6 if the number is divisible by 2 and by 3.
8 if the number formed by the last three digits is divisible
by 8.
9 if the sum of the digits is divisible by 9.
10 if the last digit is 0.
12 if the number is divisible by 3 and by 4.
Run See Slope.
Runoff election
An attempt to obtain a majority vote by eliminating one
or more alternatives and voting again on the remaining choices.
