Positive rational number

rational number

zero

Finite Decimals and Infinite Cyclic Decimals

real number

Negative rational number

Positive irrational number

unreasonable

Infinite non-repeating decimal

Negative irrational number

2. Irrational number

When understanding irrational numbers, we should grasp the moment of "infinite non-circulation", which can be summarized into four categories:

(1) An inexhaustible number, such as

Wait;

(2) Numbers with specific meanings, such as pi, or simplified numbers with pi, such as

+8 and so on;

(3) Numbers with specific structures, such as 0.101001001… etc.

(4) some trigonometric functions, such as sin60o, etc.

Test Center 2, Reciprocal, Reciprocal and Absolute Value of Real Numbers

(3 points)

1, reciprocal

A real number and its inverse are a pair of numbers (only two numbers with different signs are called inverse numbers, and the inverse of zero is zero). Seen from the number axis, the points corresponding to two opposite numbers are symmetrical about the origin. If a and b are opposites, then A+B = 0, A =-B, and vice versa.

2. Absolute value

The absolute value of a number is the distance between the point representing the number and the origin. When the absolute value of | a | ≥ 0.0, it can also be regarded as its inverse number. If |a|=a, then a ≥ 0; If |a|=-a, then a≤0. Positive numbers are greater than zero, negative numbers are less than zero, positive numbers are greater than all negative numbers, and two negative numbers, the absolute value of which is larger is smaller.

Step 3 count down the seconds

If A and B are reciprocal, there is ab= 1, and vice versa. The reciprocal is equal to its own number, which is 1 and-1 respectively. Zero has no reciprocal.

Test center 3, square root, arithmetic square root, cube root

(3- 10 integral)

1, square root

If the square of a number is equal to a, then this number is called the square root (or quadratic follow) of a.

A number has two square roots, which are in opposite directions; The square root of zero is zero; Negative numbers have no square root.

The square root of a positive number is recorded as "

".

2. Arithmetic square root

The positive square root of a positive number is called the arithmetic square root of a, and it is recorded as "

".

Positive numbers and zeros have only one arithmetic square root, and the arithmetic square root of zero is zero.

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