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radian

radicala unit of plane angular measurement that is equal to the angle at the center of a circle subtended by an arc whose length equals the radius or approximately 180°/π ~ 57.3 degrees.

radical expressionsThe √ symbol that is used to denote square root or nth roots

√

radiusan nth root of a number x is a number r which, when raised to the power n, yields x^{n}√x

random numberDistance from the center of a circle to the edge

C/2π

random samplinga number chosen by chance

random testa part of the sampling technique in which each sample has an equal probability of being chosen

random variableselecting people for a test arbitrarily

rangea variable whose value is unknown or a function that assigns values to each of an experiments outcomes

rankDifference between the largest and smallest values in a number set

rankinethe data transformation in which numerical or ordinal values are replaced by their rank when the data are sorted.

ratean absolute scale of thermodynamic temperature named after the University of Glasgow engineer and physicist Macquorn Rankine

rate of returnthe ratio between two related quantities in different units. A measure, quantity, or frequency.

ratiothe gain or loss of an investment over a specified period of time, expressed as a percentage of the investments cost.

rational exponentsindicates how many times one number contains another

rational expressionsexponents that can be expressed in the form of p/q, where q ≠ 0.

rational numberQuotient of two polynomials

P(x)/Q(x)

rational root theorema number that can be expressed as the quotient or fraction p/q of two integers

rational zero theoremused to find the rational solutions of a polynomial equation

rayused to find the rational roots of a polynomial function

real numbera part of a line that has a fixed starting point but no endpoint

reaumura value of a continuous quantity that can represent a distance along a line.

rebound ratioelating to or conforming to a thermometric scale on which the boiling point of water is at 80° above the zero of the scale and the freezing point is at zero.

receivablehow high the ball bounces after a static number of bounces,

Downward Distance at time n = h(1 - rr%^{n})/(1 - rr%)

receivables ratiothe money a company's customers owe for goods or services they have received but not yet paid for.

reciprocalmeasures the efficiency with which a company is able to collect on its receivables or the credit it extends to customers

rectanglea number which when multiplied by x yields the multiplicative identity, 1

rectangle word problema quadrilateral with four right angles

rectangulara mathematical problem expressed entirely in words involving rectangle area or perimeter typically used as an educational tool

rectangular formA 4-sided flat shape with straight sides where all interior angles are right angles (90°).

rectangular solidan equation composed of variables like x and y which can be graphed on a regular Cartesian plane.

recursive algorithma 3 dimensional object with six sides, all of which are rectangles

reduced digit suman algorithm which calls itself withsmaller (or simpler)input values, and which obtains the result for the current input by applying simple operations to the returned value for the smaller (or simpler) input.

reduced row echelonsum all the digits until the sum < 10

reducing fractionsa matrix if and only if it is in row echelon form, all its pivots are equal to 1 and the pivots are the only non-zero entries of the basic columns.

reference angledivide both the numerator and denominator by the GCF

reflectthe smallest possible angle made by the terminal side of the given angle with the x-axis.

reflexive propertya flip creating a mirror image of the shape

regressiona number is always equal to itself

a = a

regroupinga set of statistical processes for estimating the relationships between a dependent variable and one or more independent variables.

relative coordinatesmake groups of ten when performing operations such as addition or subtraction.

relative errorcoordinates specified in relation to previous coordinates

reliabilitythe ratio of the absolute error of a measurement to the measurement being taken.

remainderthe overall consistency of a measure

repeating decimalThe portion of a division operation leftover after dividing two integers

repunit numbersa decimal fraction in which a figure or group of figures is repeated indefinitely, as in 0.1111

reservenumbers that only contain 1s for digits

reserve ratioTo save something or set it aside for future use.

resistancethe portion of reservable liabilities that commercial banks must hold onto, rather than lend out or invest

resistorthe property of any object or substance of resisting or opposing the flow of an electrical current.

R = V/I

resistor color codesa passive two-terminal electrical component that implements electrical resistance as a circuit element

returncolour code used to denote the tolerance rating of a resistor is given

revenuea performance measure used to evaluate the efficiency of an investment or compare the efficiency of several investments.

revolutionthe money generated from normal business operations, calculated as the average sales price times the number of units sold

rgbA 360° angle, a full rotation, a complete turn so it points back the same way.

rhoan additive color model in which the red, green, and blue primary colors of light are added together in various ways to reproduce a broad array of colors.

rhombusA letter of the greek alphabet used for math notation.

Ρ ρ

right anglea quadrilateral with both pairs of opposite sides parallel and all sides the same length

right triangleangle measuring 90 degrees

rise over runtriangle in which one angle is a right angle

riskanother way to say slope

risk free rateexpose (someone or something valued) to danger, harm, or loss.

roman numeralthe rate of return offered by an investment that carries zero risk

rootany of the letters representing numbers in the Roman numerical system: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. In this system, a letter placed after another of greater value adds (thus XVI or xvi is 16), whereas a letter placed before another of greater value subtracts (thus XC or xc is 90).

root mean squareValue where a function equals zero

roster notationthe square root of the mean square of the set

rot13a simple mathematical representation of the set in mathematical form

rotatesimple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet.

roulettea motion of a certain space that preserves at least one point.

roundinga gambling game in which a ball is dropped onto a revolving wheel ( roulette wheel ) with numbered compartments, the players betting on the number at which the ball will come to rest.

royal flushreplacing a number with an approximate value that has a shorter, simpler, or more explicit representation

ruffinis rulea straight flush including ace, king, queen, jack, and ten all in the same suit, which is the hand of the highest possible value when wild cards are not in use.

rule of 72an efficient method of dividing a polynomial by a linear factor, with or without a remainder.

rule of producta simplified formula that calculates how long it will take for an investment to double in value, based on its rate of return.

t ~ 72/i

rule of successionIf there are n(A) ways to do A and n(B) ways to do B, then the number of ways to do A and B is n(A) × n(B)

n(A) × n(B)

run length encodinga formula introduced in the 18th century by Pierre-Simon Laplace in the course of treating the sunrise problem

(s + 1)/(n + 2)

a form of lossless compression