Online Math Dictionary: R
Easy to understand math definitions for KAlgebra mathematics
Just scroll down or click on the word you want and I'll scroll down for you!
Radian A radian is a special unit of measure (like degrees) that measures things that are circular  like angles that sweep around! You start using radians in trigonometry. To find out more info about radians, check out my Trigonometry of Circlespage. 
Radical
A radical is a root (like a square root) of a number. A radical is made up ofradical sign and something inside called the radicand.
Example:
To learn more about radicals, check out my Radicals Review lesson.
Radicand The radicand is the thing inside the radical sign. 


Ratio The ratio you've probably heard the most is "miles per hour"... This is really a fraction with miles in the numerator andhours in the denominator. In the example below, if you've driven 180 miles in 3 hours, that's a ratio of 60 miles perhour.


Rational Number A rational number is a number that can be written as a fraction with integers as the numerator and denominator. This includes fractions, regular counting numbers, negative numbers, terminating decimals and repeating decimals. 

Rationalize the Denominator 



Real Numbers The set of Real Numbers consists of both the rational and irrational numbers. 

Reciprocal of a Number The reciprocal of a number is the number you need to multiply by to get 1 as the answer. The numbers below are reciprocals of each other. 





Regular Polygon Regular polygons are polygons whose sides are the same length and whose angles are the same size. Below is aregular triangle (which is called an equilateral triangle), a regular quadrilateral (which is a square), a regular pentagon, a regular hexagon and a regular heptagon. 

Relation A relation is an ordered pair in the form: (x, y) Example: (2, 3) Ordered pairs are used as rectangular coordinates. 

Relatively Prime Two numbers are relatively prime if they have no common factors other than the number 1. Another way to define it is to say that two numbers are relatively prime if their greatest common divisor is 1. Examples: 9 and 14 are relatively prime since their greatest common divisor is 1... 4 and 18 are NOT relatively prime since their greatest common divisor is 2. 

Remainder The remainder is what might be "left over" when you are doing a division problem. For example, 3 goes into 17 five times with 2 left over... So, the remainder is 2. We write this as 

Repeating Decimal A repeating decimal is a decimal where the decimal part repeats. This means that one or more numbers just keep showing up over and over again. We put a bar over the repeating part: Repeating decimals can always be converted into fractions. Repeating decimals are a rational numbers. 







Root of a Polynomial The roots of a polynomials are the solutions when the polynomial is set equal to zero. This is a bit too complicated for a short definition, so check out my Zeros of a Polynomials lesson. 
A  B  C  D  E  F  G  H  I  no J's 
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N  O  P  Q  R  S  T  U  V  W  no X's 
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