# Mathematical Symbols (Part 2)

 Symbol Name Explanation Q rational numbers When we divide an integer (a) by another integer (b) we get a rational number. Every rational number is represented by an integer part. and a fractional part. The letter Q is derived from the English word. quotient, which means quotient, since a rational number is a quotient of two integers.For example, if a = 6 and b = 2, we get the rational number 3.0. If a = 1 and b = 2, we get the rational number 0.5. Both have a finite number of places after the comma and are called rationals of exact decimal.There are cases where the number of squares after the comma is infinite. For example, a = 1 and b = 3 gives us the rational number 0,33333… It's called periodic tithe. We can assume that rational numbers encompass all integers and those that lie in the intervals between integers.Q = {a / b | The Z and b Z *}.Remember that There is no division by zero!.The symbol Q * is used to indicate the set of non-null rational numbers:Q * = {x Q | x 0}The symbol Q + is used to indicate the set of nonnegative rational numbers:Q + = {x Q | x 0}The symbol Q- is used to indicate the set of non-positive rational numbers: Q- = {x Q | x 0}The symbol Q * + is used to indicate the set of positive rational numbers:Q * + = {x Q | x> 0}The symbol Q * - is used to indicate the set of negative rational numbers:Q * - = {x Q | x <0} I irrational numbers These are real numbers that cannot be obtained by dividing two integers, that is, they are real numbers, but not rational. These numbers have infinite houses after the comma, which do not repeat periodically. The most famous irrational number is pi ( ). R real numbers The set of all rational and irrational numbers is the set of real numbers, indicated by R.We indicate by R * the set of real numbers without zero, that is, the symbol R * is used to represent the set of nonzero real numbers: R * = R - {0}The symbol R + is used to indicate the set of nonnegative real numbers:R + = {x R | x 0}The symbol R- is used to indicate the set of non-positive real numbers:R- = {x R | x 0}The symbol R * + is used to indicate the set of positive real numbers:R * + = {x R | x> 0}The symbol R * - is used to indicate the set of negative real numbers:R * - = {x R | x <0} Ç complex numbers A complex number is represented by a + bi being The the real part and B the imaginary part.Imaginary unit: defines the imaginary unit, represented by the letter i, as being the square root of -1. You can then write: i = (-1). Comparation It's smaller than, it's bigger thanx < y it means that x it's smaller than yx > y it means that x is bigger than y and Comparation is less than or equal to, is greater than or equal tox y means: x is less than or equal to y;x y means: x is greater than or equal to y