Definition of all junior high school mathematics

Now bookstores sell a kind of pocket book, a small book, specialized in summarizing the definition of the key points of each subject. One book sums up all the contents of Junior (Senior) middle school three years, which is very comprehensive. There are also some ways to remember the knowledge points skillfully, and the price is not expensive, which is very good. If you want to review, it is suggested to buy one

On the definition of N multi concepts in junior high school mathematics
Ah, I have to memorize this
Let's start with that
The concept of square root, approximate number and significant number, the arithmetic of addition, subtraction, multiplication and division of real number
The concept of quadratic radical and the arithmetic of addition, subtraction, multiplication and division, and the four simple operations of real numbers
The meaning of numbers expressed by letters, the meaning and basic properties of exponential powers of integers, the concept of integral fractions
Criteria for integral addition and subtraction and multiplication
PS: just answer as many as you can OK, I'll add points

Square root, also known as quadratic root, for non negative real number, refers to a real number whose self multiplication result is equal to (√). The square root belonging to non negative real number is called arithmetic square root. A number is close to the accurate number (slightly more or less than the accurate number), which is called approximate number. Significant number refers to the number in the analysis work

Triangle trapezoid parallelogram diamond square circle
What are the area formulas?
What are the concepts of positive and negative numbers

Positive number
Positive number
If a number x > 0, it is said to be a positive number
negative
Negative
Less than zero（

In △ OAB, vector OA = (1,2), vector ob = (- 2,1), and vector od is the high of vector ab. if vector ad = λ, vector AB, then the value of real number λ
I would like to ask if the idea of this problem starts from the vector OD ⊥ vector AB, and we need to work out the coordinates of D.

Sure, but we can only find the relationship between abscissa and ordinate with this

Some questions about trigonometric function
1、 Find the domain of definition
1. Y = radical (- cosx) + radical (ctgx)
2.y=ctg(sinx)
3. Y = radical (2 + Log1 / 2x) + radical (TGX)
2、 If SiNx + siny = 1, cosx + cosy = 1 / 2, find SiNx

1. To make the result in the root greater than zero, that is, cosx in the first root

Why is the pronunciation of a word in a dictionary a problem

Because the word "one" has only one pronunciation, in order to read aloud in a specific language environment, sometimes "tone sandhi" is needed. When the last word is four tones, "one" is read as two tones; when the last word is one tone, "one" is read as four tones

In the parallelogram ABCD, AC is a diagonal line, ∠ B = ∠ DAC, extend BC to point E, make CE = BC, connect De, try to explain: the parallelogram abed is isosceles

It is proved that ABCD is a parallelogram, ∠ B = ∠ ADC
Because ∠ B = ∠ DAC, ∠ DAC = ∠ ADC.AC=CD
Because AB = CD, AC = ab
In △ ABC and △ DCE
AB=CD,
AB‖CD,∠ABC=∠DCE
BC=CE
So △ ABC ≌ DCE
AC = de. so AB = De
Quadrilateral abed, ad ‖ be, ab = De, and ab is not parallel to de
So it's isosceles trapezoid

English words for buses

Bus, you can try to find the New Oxford Dictionary, there may be synonyms

It is known that the triangle ABC is an acute triangle, AB > AC, CD is perpendicular to AB and D. can you explain that BC squared = AB squared + AC squared - 2Ab * ad
It should be
Brother, what I asked is an acute triangle, not a right triangle!

For example, according to the right triangle: BC square = CD square + DB square, AC square = ad square + DC square, by subtracting the two formulas: BC square - AC square = DB square - ad square, BC square = AC square + (db-ad) * (DB + AD) = AC square + (DB

I like fruit, but I don't like vegetables

Jane likes fruit,but She doesn’t like vegetables.

Definition of all junior high school mathematics