If cosa / radical (1 + Tan ^ 2a) + Sina / radical (1 + cot ^ 2A = - 1), then a is in the___ quadrant

If cosa / radical (1 + Tan ^ 2a) + Sina / radical (1 + cot ^ 2A = - 1), then a is in the___ quadrant

In the third quadrant, the one after | Cosa | = 1 / sqrt (1 + Tan ^ 2a) is the same. It's easy to think that only - cos ^ 2A - Sin ^ 2A = - 1

A small party is composed of six programs. In the performance season, Mu a must be in the first two places, program B cannot be in the first place, and program C must be in the last place. All kinds of arrangement schemes are required
The answer is a (1,3) times a (3,3) + a (4,4) = 42

First row C, because he must be last, so there is only one way, 1
Row a again, because a can only be in the first two places, and whether he is in the first place or not is related to B's arrangement (because B can't be in the first place),
So in case 1, a is in the first place, a and C are sure, and B will not be in the first place, so the remaining four programs are all arranged (B is also included)
A(4,4)=4*3*2*1=24
Situation 2: if a is in the second place, then it needs a program to go out, and B takes the first place. There are three kinds of programs
Then the remaining three programs (including B) are arranged in a (3,3) = 3 * 2 * 1 = 6, so the total number of times = 3 * 6 = 18
So it adds up to 18 + 24 = 42

There are 2n small balls of type A and 2m small balls of type B. how many ways can these balls be arranged in a circle? What about 2n + 1 a 2m + 1 B? What about 2n a 2m + 1 B?

That is to say, arrange in 2n + 2m balls
The arrangement methods are as follows
A(2n+2m)(2n+2m)
Corresponding
A(2n+1+2m+1)(2n+1+2m+1)
A(2n+2m+1)(2n+2m+1)

Give me formulas, theorems
Formula, theorem proof things, such as triangles and trapezoids, and Pythagorean theorem, all junior high school can add scores

The proof problem in mathematics is really not difficult. The key is the thought of reverse deduction. If you think that the answers are all given to you, it's hard for you to make up a process. The key is to master the knowledge points of the chapter, know some formulas that must be used, and then do more. When you encounter a proof problem, you can see which formula can be used, and then combine forward and reverse deduction, Certainly can improve! If you want to learn mathematics well, it needs you to spend more effort to make clear the knowledge points of each chapter, and then do more exercises, so that you can flexibly use the formula! In addition, it is recommended that you buy a reference book, which has a summary of the knowledge points of each chapter, plus practice, it is recommended that you after each exam, If it's careless, you should be careful in calculation and process. This is the key. The exam is to test who is most careful, and those who get small questions will win the world. If you can't do it, then after mastering the knowledge points of each chapter, you should practice more, practice makes perfect! Finally, you should be careful. In fact, those who learn mathematics well don't necessarily get high marks, You will find that you have mastered this chapter, but you can't do well in the exam because you haven't mastered the really useful exam skills. The key is to be careful. The exam depends on who is most careful. If you do it slowly, there will be unexpected gains. I believe you will succeed and learn mathematics well. Come on!

I want a complete set of high school mathematics knowledge summary, the best example

In those days, there was a set of books called key and difficult points manual. We used to go to school. I don't know if it's still popular now
You go to the bookstore to have a look. Now there are many books. You can find them in the review materials of college entrance examination. They are all comprehensive

Book 2, review on page 33, reference B, question 7
If the inequality ax ^ 2 + BX + C about X

Correction: ax ^ 2 + BX + C

About the junior high school circle mathematical formula and auxiliary line method, do the problem idea
Know how to calculate the arc length and sector area for radius and center angle, and how to calculate the generatrix length, center angle, radius and side area of cone For a long time, there has been some confusion about the calculation formulas of these circles and cones, and some of them are not clear. I hope you can give me the sum of these formulas. It's better to have some language notes,
When you get a question about a circle, I hope that you can sort out the idea of doing the question, how to think about it, what are the auxiliary line methods, and there is a sum of methods,

Base radius = base circumference / 2 μ
Bus length L = side circumference / 2 μ
Arc length = circumference of side circle / angle of expanded view
S circle = π × R & sup2;
C circle = 2 π R or π D

I always can't remember a very important formula
What is the sum of squares of the two quadratic equations of bivariate? That is, X1 square + x2 square +?
There's a mistake on it. Is it X1 square + x2 square =?

X1+X2=-b/a X1*X2=c/a
X1^2+X2^2=(X1+X1)^2-2X1*X2=b^2/a^2-2c/a

There are a lot of calculation problems in the line test. Are there any commonly used mathematical formulas?

Basic algebraic formula 1. Square difference formula: (a + b) × (a-b) = a2-b22. Complete square formula: (a ± b) 2 = A2 ± 2Ab + B2. Complete cubic formula: (a ± b) 3 = (a ± b) (A2 AB + B2) 3. Multiplication of the same base power: am × an = am + n (m, n are

What is the common mathematical formula similar to the complete square formula in senior one?
When judging whether two sets are equal or contained, we often have to deform ~! Experts, help me!

Cubic and cubic difference formula, judge the set relationship, you can use the special value detection method