A few math problems, some difficult, please ask the masters

I won't count the rest of it.

Oh, and after reading the answer to Question 2 of Snow 9 in Syracuse, I had to write a few more sentences. His algorithm is so stupid. Maybe he didn't think about it, then I'm idle, expand it, hehe.

Method 1 recommends a method, I think it makes a lot of sense!

You draw a square. Then divide it evenly. That is, two 1 2, and then divide. i.e. 1 4....Dividing it, you can get the answer, and it occurred to me that this method is not suitable for exams, but it is of great significance. Geometry and numbers are combined

Law 2 um. It can be solved with Snow 9 in Syracuse, but it is too cumbersome, so you can make 1 64 a and 1 32 2a, and push each other in turn.

3 questions, Snow 9 method in Syracuse is very good.

3 Question sA sB = 6 5; t A t B = 8 9 v A v B = (s A t A) (s B t B) = 27 20

I didn't understand the first sentence in the first question.

Question 1. Solution: Set up the water tank to fill the ridge when the total width of the digging Zen water x liters, according to the meaning of the topic.

5 6)*x*80%-(5 6)*x*20%=210.

5/6）*x*60%=210

The solution is x=420 (liters).

Question 2. Solution: If the amount of corn harvested in the previous year is x, the amount of corn harvested last year is x* (1+25%); Therefore, the result sought is:

x/(x*（1+25%))100%=（100/125）*100%=80%

According to the sinusoidal theorem, sina bc=sinc ab

Then the tree height ab=bcsinc sina can bring in the data.

Let the height of the tree be x, then.

Root number 3*x-x=10

x=5*root number 3+5

ab = root number 2x = 5 * root number 6 + 5 root number 2 = meter.

or root number 3*x+x=10

x=5*root number 3+5

ab = root number 2x = 5 * root number 6 + 5 root number 2 = meter.

Author: Tiramisu 620 - Level 1 2007-6-3 19:07

To do this question, we must first know the speed of A and B, and I don't know here, so I can only set the speed of A to A and the speed of B to B, and let it take X hours for A and B to reach place C.

Columnar formula (x+ solution gives x=

Suppose the distance between the two places is s, and the time used by A and B to meet is t, and the speed of A is s (t+

B's velocity is s (t+5).

The sum of the velocities of A and B is s t

i.e. s (t+

Eliminate s on both sides, and then divide to find t=4

Therefore, it takes T+ hours to complete the journey of Line A.

It takes t+5=9 hours to complete the second line.

There is a clever solution to this question.

Car A and car B meet at point C, and let the time it takes for them to meet is t, and because the time required for the complete journey of line A is: t + the time required for the complete journey of line B: t+5

So A takes fewer hours than B.

Let the speed of vehicle A be a and the speed of vehicle B be b

5b=at ②

②：a:b=5:4

So, ac:bc=5:4

Because B takes 5 hours in the AC section, it takes 4 hours in the BC section, so the whole journey in line B takes 9 hours.

And because A uses less hours, so: A uses the whole process: hours).

1.= Are you sure you made a mistake? What does cos2 2 mean What is the letter after cos?

5.(sina + cosa) = 1 + sin2a = 1 3 then sin2a = -2 3

and a is the second quadrant angle then cos2a = 5 3

2.From the meaning of the title sina-cosa>0 and tana>0sina-cosa>0 2sin(a- 4)>o from 2sin(a- 4)>o a- 4 0 , 2 3 2,2

a 4 ,3 4 7 4 ,9 2 from tana>0 a 0 , 2 3 2 In summary, there is a 4 , 2 7 4 ,3 2 3Is the third one wrong: should it be y=sin(2x+2 3)?

The answer is y=|sinx|