The second chapter of senior two mathematics is a summary of mind map. The second chapter of senior two mathematics: the concept and classification of real numbers 1, the classification of real numbers.
First, the classification is: positive number, negative number, 0;
Another classification is: rational numbers and irrational numbers.
Combine two categories: negative rational number, negative irrational number, 0, positive rational number and positive irrational number.
2. Irrational number: Infinitely circulating decimals are called irrational numbers.
Should we grasp irrational numbers when we understand them? Infinite loop? At that time, there were four categories:
(1) An inexhaustible number, such as;
(2) Numbers with specific meanings, such as pi? , or simplified to include? The number of, such as+8;
(3) Numbers with specific structures, such as 0.1010010001? Wait;
(4) Some trigonometric function values, such as sin60o, etc.
The second chapter of the second grade mathematics: reciprocal, reciprocal, absolute value 1, reciprocal of real numbers.
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 and a=? B, and vice versa
2. Absolute value
On the number axis, the distance between the point corresponding to a number and the origin is called the absolute value of the number. (|a|？ 0)。 The absolute value of zero is itself and can also be regarded as its inverse. If |a|=a, then a? 0; If |a|=-a, then a? 0.
Step 3 count down the seconds
If A and B are reciprocal, there is ab= 1, and vice versa. The numbers whose reciprocal equals itself are 1 and-1. Zero has no reciprocal.
4. Counting axes
The straight line that specifies the origin, positive direction and unit length is called the number axis (pay attention to the three elements specified above when drawing the number axis).
When solving problems, we should really master the idea of combining numbers with shapes, understand the one-to-one correspondence between real numbers and points on the number axis, and use them flexibly.
Step 5 estimate