Math Glossary Letter R radian noun a 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 noun The √ symbol that is used to denote square root or nth roots√ radical expressions noun an nth root of a number x is a number r which, when raised to the power n, yields xn √x radius noun Distance from the center of a circle to the edgeC/2π random number noun a number chosen by chance random sampling verb a part of the sampling technique in which each sample has an equal probability of being chosen random test noun selecting people for a test arbitrarily random variable noun a variable whose value is unknown or a function that assigns values to each of an experiments outcomes range noun Difference between the largest and smallest values in a number set rank noun the data transformation in which numerical or ordinal values are replaced by their rank when the data are sorted. rankine noun an absolute scale of thermodynamic temperature named after the University of Glasgow engineer and physicist Macquorn Rankine rate noun the ratio between two related quantities in different units. A measure, quantity, or frequency. rate of return noun the gain or loss of an investment over a specified period of time, expressed as a percentage of the investments cost. ratio noun indicates how many times one number contains another rational exponents noun exponents that can be expressed in the form of p/q, where q ≠ 0. rational expressions noun Quotient of two polynomialsP(x)/Q(x) rational number noun a number that can be expressed as the quotient or fraction p/q of two integers rational root theorem noun used to find the rational solutions of a polynomial equation rational zero theorem noun used to find the rational roots of a polynomial function ray noun a part of a line that has a fixed starting point but no endpoint real number noun a value of a continuous quantity that can represent a distance along a line. reaumur noun elating 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. rebound ratio noun how high the ball bounces after a static number of bounces,Downward Distance at time n = h(1 - rr%n )/(1 - rr%) receivable noun the money a company's customers owe for goods or services they have received but not yet paid for. receivables ratio noun measures the efficiency with which a company is able to collect on its receivables or the credit it extends to customers reciprocal noun a number which when multiplied by x yields the multiplicative identity, 1 rectangle noun a quadrilateral with four right angles rectangle word problem noun a mathematical problem expressed entirely in words involving rectangle area or perimeter typically used as an educational tool rectangular noun A 4-sided flat shape with straight sides where all interior angles are right angles (90°). rectangular form noun an equation composed of variables like x and y which can be graphed on a regular Cartesian plane. rectangular solid noun a 3 dimensional object with six sides, all of which are rectangles recursive algorithm noun an algorithm which calls itself with smaller (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 digit sum noun sum all the digits until the sum < 10 reduced row echelon noun a 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. reducing fractions noun divide both the numerator and denominator by the GCF reference angle noun the smallest possible angle made by the terminal side of the given angle with the x-axis. reflect noun a flip creating a mirror image of the shape reflexive property noun a number is always equal to itselfa = a regression noun a set of statistical processes for estimating the relationships between a dependent variable and one or more independent variables. regrouping verb make groups of ten when performing operations such as addition or subtraction. relative coordinates noun coordinates specified in relation to previous coordinates relative error noun the ratio of the absolute error of a measurement to the measurement being taken. reliability noun the overall consistency of a measure remainder noun The portion of a division operation leftover after dividing two integers repeating decimal noun a decimal fraction in which a figure or group of figures is repeated indefinitely, as in 0.1111 repunit numbers noun numbers that only contain 1s for digits reserve noun To save something or set it aside for future use. reserve ratio noun the portion of reservable liabilities that commercial banks must hold onto, rather than lend out or invest resistance noun the property of any object or substance of resisting or opposing the flow of an electrical current.R = V/I resistor noun a passive two-terminal electrical component that implements electrical resistance as a circuit element resistor color codes noun colour code used to denote the tolerance rating of a resistor is given return noun a performance measure used to evaluate the efficiency of an investment or compare the efficiency of several investments. revenue noun the money generated from normal business operations, calculated as the average sales price times the number of units sold revolution noun A 360° angle, a full rotation, a complete turn so it points back the same way. rgb noun an 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. rho noun A letter of the greek alphabet used for math notation.Ρ ρ rhombus noun a quadrilateral with both pairs of opposite sides parallel and all sides the same length right angle noun angle measuring 90 degrees right triangle noun triangle in which one angle is a right angle rise over run noun another way to say slope risk noun expose (someone or something valued) to danger, harm, or loss. risk free rate noun the rate of return offered by an investment that carries zero risk roman numeral noun any 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 noun Value where a function equals zero root mean square noun the square root of the mean square of the set roster notation noun a simple mathematical representation of the set in mathematical form rot13 noun simple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet. rotate noun a motion of a certain space that preserves at least one point. roulette noun a 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. rounding verb replacing a number with an approximate value that has a shorter, simpler, or more explicit representation royal flush noun a 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. ruffinis rule noun an efficient method of dividing a polynomial by a linear factor, with or without a remainder. rule of 72 noun a 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 product noun If 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) rule of succession noun a formula introduced in the 18th century by Pierre-Simon Laplace in the course of treating the sunrise problem(s + 1)/(n + 2) run length encoding verb a form of lossless compression