Title 
Description 

Radian 
A Radian is an angle (measure) that subtends an arc length (on a circle) equal to the radius of the circle. Radians are just as good as degrees for measuring angles, and sometimes better.


Radian Measure 
Radian Measure is just as good as degree measure for angles, and sometimes better. Pi radians are equivalent to 180 degrees.


Radical 
A root symbol or the root itself is sometimes termed a Radical.


Radicand 
A number taken to a root is a Radicand; the number under a root sign.


Radius 
Onehalf the diameter of a circle is the Radius. It is the distance from the center of a circle to any point on the circle.


Range 
We may speak of a Range of values as simply the difference between high and low values of a data set. More specifically, the values generated by the input of domain values into a function map into the Range of values of the function.


Ratio 
Sometimes Ratio is meant to state a constant proportion. More generally, the Ratio of two real values is the quotient of one number divided by the other.


Rational 
A Rational number can be expressed as the ratio of two integers. When expressed as a decimal, a Rational number will either repeat or terminate (with repeating zeros).


Rational Expression 
Mathematical statements written as fractions with a numerator and a denominator are often termed Rational Expressions.


Ray 
A set of collinear points, a Ray has an endpoint and proceeds infinitely far in a single direction.


Real Number 
Depicted on the Real Number line, such a value is either less than, equal to, or greater than every other real value.


Reciprocal 
Every nonzero real value has a Reciprocal. A number and its Reciprocal multiply to one. We may find a Reciprocal of a number by dividing it into 1.


Rectangle 
A quadrilateral with many special properties, including all those of a parallelogram, and then some.


Rectangular Coordinates 
The familiar xy coordinate plane; Cartesian Coordinates.


RectangularPolar Conversion 
A simple algorithm to change (x, y) into (r, theta).


Recursive 
A Recursive formula or series has successive terms defined by operations or permutations on the term.


Reference Angle 
In standard position, any angle in quadrants II, III, or IV has a Reference Angle equal to the acute angle made with the xaxis.


Reflexive 
Literally "in relation to itself." When we say A = A, we employ a Reflexive property.


Regression 
A statistical method of evaluating leastsquares to find a bestfit line or curve to data.


Regression Line 
To find a bestfit linear relation with scatterplot data, we use Linear Regression to find a Regression Line.


Regular Polygon 
A Regular Polygon is both equilateral (all sides congruent) and equiangular (all angles congruent).


Regular Polyhedron 
A geometric solid with all faces regular polygons.


Regular Prism 
A Prism with bases of Regular polygons.


Regular Pyramid 
A Pyramid with a base of a Regular polygon.


Regular Right Prism 
A Prism with bases of Regular polygons and lateral faces perpendicular to those bases.


Regular Right Pyramid 
A Pyramid with a Regular polygon for a base and an apex directly above the center of the base.


Relative Maximum 
Also a local Maximum, a high spot on the graph of a function. It is the greatest value within a defined neighborhood.


Relative Minimum 
Also a local Minimum, a low spot on the graph of a function. It is the least value within a defined neighborhood.


Relatively Prime 
Two integers with no common factors other than one are said to be Relatively Prime.


Remainder 
When a divisor does not divide evenly into the dividend, we have a Remainder.


Revolutions Per Minute 
Abbreviated "rpm" it conveys the number of complete circular rotations that occur every 60 seconds at some constant rate of revolution.


Rho 
Lowercase Rho, the 17th letter of the Greek alphabet, is often used for density (mass per unit volume) in physics.


Rhombus 
A quadrilateral with four congruent sides. Its diagonals are perpendicular.


Riemann Sum 
Effectively the definite integral in calculus.


Right Angle 
An angle of 90 degrees or pi/2 radians. Perpendicular lines meet at Right Angles.


Right Circular Cone 
A cone with a circular base and an apex directly above the center of the base.


Right Circular Cylinder 
A circular cylinder with sides orthogonal to parallel bases. 

Right Cone 
Any Cone, circular or otherwise, with its apex directly above the center of the base.


Right Cylinder 
Any Cylinder, circular or otherwise, with lateral sides orthogonal to the bases.


Right Prism 
A Prism with lateral sides orthogonal to the bases.


Right Pyramid 
A Pyramid with its apex directly above the center of the base.


Right Regular Prism 
A Prism with bases of Regular polygons and lateral faces perpendicular to the bases.


Right Regular Pyramid 
A Pyramid with a Regular polygon for a base and an apex directly above the center of the base.


Right Square Parallelepiped 
Cube. 

Right Square Prism 
A cube, or a shoebox if the ends of the shoebox are square.


Right Triangle 
A triangle with a right angle.


Rolle's Theorem 
A principle from firstsemester calculus that asserts a first derivative of zero exists on a smooth, continuous, differentiable function between constant range values.


Root Mean Square 
Abbreviated RMS it is the square root of the arithmetic mean of the squares of some real values, as from a data set.


Root, Number 
The Root of a given Number is the value that raised to the power of the root returns the given number.


Rotation 
Movement in a circulation or circular fashion, often around a point or an axis, is termed Rotation.


Rounding 
Not exactly truncating, rounding involves reduction in the precision of a value to approximate that value to some exact value with less precision.


Row Operations 
Arithmetic Operations on the Rows of a matrix to solve simultaneous equations.


RowEchelon Matrix 
A Matrix upon which Row operations have been performed.

