Prime number, also known as prime number, refers to a number that can only be divisible by 1 and itself. For example, 2,3,5,7, 1 1 ...

Complex number means that there are other divisors besides 1 and itself, such as 4. In addition to 1 and 4, it can be divisible by 2.

2. Common factor, greatest common divisor and least common multiple

Common factor, also known as common factor, is called common factor if there are the same factors between two or more natural numbers. Any two natural numbers have a common factor 1. (except zero) and the largest of these common factors is called the greatest common factor of these positive integers.

To find the greatest common factor of several integers, just multiply all their prime factors, and the product is their greatest common factor.

3. Real and imaginary numbers

The square root of a negative number has no solution in the real number range.

Mathematicians call the result of this operation an imaginary number, because such an operation cannot be explained in the real number range, so it is called an imaginary number.

A pair of numbers consisting of real numbers and imaginary numbers is regarded as a number within the range of complex numbers, so it is called a complex number.

Thus, the real number becomes a special complex number (lacking ordinal number), and the imaginary number also becomes a special complex number (lacking real number).

The imaginary number I, the unit of I, means that the root sign is negative 1.

3i is an imaginary number, that is, the root sign (-3), that is, the root sign (-1).

2+3i is a complex number (the real part is 2 and the imaginary part is 3i).

Complex number is different from imaginary number, and it is a+bi number. Where a and b are real numbers, and I is a number satisfying I2 =- 1. Because the square of any real number is not equal to-1, I is not a real number, but a new number other than a real number. In the complex number A+Bi, A is called the real part of the complex number, B is called the imaginary part of the complex number, and I is called the imaginary part. When the imaginary part is equal to zero, this complex number is a real number; When the imaginary part is not equal to zero, this complex number is called imaginary number, and if the real part of imaginary number is equal to zero, it is called pure imaginary number. As can be seen from the above, complex set contains real set, so it is an extension of real set.

4. Rational numbers and irrational numbers

Rational number: a number that can be accurately expressed as the ratio of two integers.

For example, 3, -98. 1 1, 5.72 ... and 7/22 are rational numbers.

Integers and fractions are rational numbers. Rational numbers can also be divided into positive rational numbers, 0 and negative rational numbers.

Irrational numbers refer to infinite cyclic decimals.

Non-negative integer sets (or natural number set) are those recorded as n?

N-0 and natural numbers, such as 0. 1。 2。 3。 . .

What are the positive integer sets called N+?

N+- positive integer, such as 1. 2。 3。 . . .

What are the integer sets that Z refers to?

Z-positive and negative integers and 0, for example. . . -2。 - 1。 0。 1。 2。 3。 . .

What are the real number sets labeled R?

R-rational number and irrational number

Infinitely cyclic decimals and numbers with infinite roots are called irrational numbers.

Integers and fractions are collectively called rational numbers.

Mathematically, a rational number is the ratio of two integers, usually written as a/b, where b is not zero. Fraction is a common expression of rational number, while integer is a fraction with denominator of 1, which is also a rational number.

Mathematically, a rational number is the ratio of an integer a to a non-zero integer b, which is usually written as a/b, so it is also called a fraction. The Greek name is λ ο γ ο? The original meaning is "rational number", but the Chinese translation is not appropriate, and it has gradually become "rational number". Real numbers that are not rational numbers are called irrational numbers.

The set of all rational numbers is expressed as q, and the fractional part of rational numbers is finite or cyclic.

5. Integers

Integer: Numbers like -2,-1, 0, 1, 2 are called integers. Integer is a number indicating the number of objects, and 0 indicates that there are 0 objects. Integer is the most basic mathematical tool that human beings can master. All integers form an integer set, which is a number ring. In the integer system, a natural number is a collective name of 0 and a positive integer, 0 is zero,-1, -2, -3, …, -n, … (n is an integer) is a negative integer. Positive integers, zero integers and negative integers form an integer system. The given integer n can be negative (n∈Z-), nonnegative (n∈Z*), zero (n=0) or positive (n ∈ z+).

With 0 as the boundary, we divide integers into three categories: 1. A positive integer, that is, an integer greater than 0, such as 1, 2,3, …, n, … 2.0, is neither a positive integer nor a negative integer. 3. Negative integers, that is, integers less than 0, such as-1.

6. Odd and even numbers

Odd (English: odd) mathematical term, in an integer, the number divisible by 2 is even, the number divisible by 2 is odd, the even number can be represented by 2k, and the odd number can be represented by 2k+ 1, where k is an integer. Odd numbers include positive and negative odd numbers.

With regard to odd numbers and even numbers, there are the following properties: (1) odd numbers will not be even numbers at the same time; Two consecutive integers must be odd and even. (2) The sum of odd numbers and odd numbers is even; The sum of even and odd numbers is odd; The sum of any number of even numbers is even. (3) The difference between two odd (even) numbers is even; The difference between even and odd numbers is odd numbers. (4) If A and B are integers, the parity of a+b and a-b is the same, that is, a+b and a-b are both odd or even. (5) The product of n odd numbers is odd, and the product of n even numbers is even; If one cis is even, the product is even, that is, a * b * c *……* ... * even * x * y = even, where a, b, c, ... x, y are integers, and the formula can be simplified as: odd * even = even. (6) Odd numbers are 1, 3, 5, 7 and 9; Even numbers are 0, 2, 4, 6 and 8. 0 is a special even number. In 2002, the International Mathematical Association stipulated that zero was an even number, and in 2004, China also stipulated that zero was an even number. Elementary school stipulated that 0 is the smallest even number, but by junior high school, I learned negative numbers. When there are negative even numbers, 0 is not the smallest even number. ) (7) The square of an odd number divided by 8 is 1.

7. Cardinality

Mathematically, radix is also called radix, which refers to a concept in set theory and describes the number of elements contained in any set. Two sets that can establish a one-to-one correspondence between elements are called reciprocal sets. For example, a set of three people and a set of three horses can establish a corresponding relationship, which is two equal sets. In addition, there are language and military bases.

8, floating point number

Floating-point numbers are digital representations of numbers belonging to a specific subset of rational numbers, which are used to approximately represent any real number in a computer. Specifically, this real number is obtained by multiplying an integer or a fixed number (mantissa) by the integer power of a cardinal number (usually 2 in a computer), similar to the cardinal number 10 used in scientific notation.

9. Boolean value

Boolean value is one of true or false. The action script will also convert the values true and false to 1 and 0 when appropriate. Boolean values are usually used with logical operators in action script statements that control script flow through comparison.