Middle school math answer process, junior high school math problem solving process

Hello! This is to find an inner angle of the triangle, you have to make full use of the sum of the inner angles of the triangle is equal to 180 degrees, which is an isosceles triangle, using the properties of the isosceles triangle, you can solve it like this: 1. The triangle abc in the angle bad+angle dac=180-angle b-angle c=180-2 angle c

2. In the triangle ADE, the angle DAE = 180-2 angle AED and the angle AED = angle C + angle EDC

3. The above formula simplifies the two angles of angle dac and angle dae are equal, and you can calculate the angle you find, angle dac=180-2 angle c-40=180-2 (angle c + angle edc) = angle dae (written very finely, understand).

So the angle EDC = 20 degrees.

To solve such a problem is to make a list of equations about the angle to be found so that it is in a triangle.

Happy to you!

Summary. Dear, you send out specific questions, and Xiaohai will answer them more clearly for you.

Dear, you send out specific questions, and Xiaohai will answer them more clearly for you.

The specific process of solving these two questions.

Dear students, which question needs to be answered?

Both require 21 and 22

Dear, the specific solution ideas for the 21 questions are as above, check.

Okay, thank you, teacher, 22 questions also need to be solved for trouble.

You can click on my avatar and click on consultation. Choose this one of the 6 times.

The infinite wheel can have several questions.

It can be up to 2 hours with no limit on the number of questions.

1. The distance is 5cm*6000000

5cm*6*10^6

3*10^7cm

3*10^5m

3*10^2km

300km, so the actual distance is 300km.

2. One-half. Reason: Each coin toss is an independent event3, perimeter increment = 2 r-2 r=2 (r-r)=2 *(3-2)=2 cm= cm

（1）5cm：x=1：6000000

x=30000000

2) 1 2 Because the texture is uniform, the probability of facing up at random is 1 2 (3) c = 2 r c increase = 2 r increase = 2 (3-2) = 2

The circumference is also 5 times that of a small circle.

The 90-degree central angle of the circle is opposed to the circumference of 1 4, so 8 4 = 2

The 45-degree central angle is 1 8 circumference, so.

Set up a transport ground x station.

The total amount of money is [500*x+(16-x)*400] + [300*(15-x)+(13-(16-x))*600].

x<=15,16-x<=13

x>=3

Simplification: 400*x+9100

Therefore, when the smallest cost is the least, x>=3So, 400*3+9100=10300 yuan.

Both: A to A to transport 3 units, B to transport 13 units, B to A transport 12 units, B to 0 units.

The cheapest to go to A is B, and the cheapest to B is A, so a B and a A. The division of labor is clear, and they are not dry with each other!

A transports 13 units to place B, transports 3 units to place A, and transports 12 units to place A.

1.From abc>0 there are two negative and one positive. Or all three. (a, b, c are not 0).

From a+b+c=0 combined with the above conclusions, it can be seen that only two negative and one positive can satisfy the condition.

Consider a>0 b<0 c<0

and a+b+c=0 So the absolute value of a>b and the absolute value of a>c. （a>-b a>-c）

So 1 a+1 b+1 c<0 (1 a<1 (-b)).

2.Solution: When the two sides of abc are long, a, b, s abc=1 2 absinc, when c=90°, the area of abc is the largest, and s abc=1 2 ab, and the square of (a-b) is 0, that is, 1 2 ab 1 4 (a square + b squared), a, s = 1 4 (a square + b squared), so this option is possible;

b, 1 2 (A square + B squared) 1 4 (A square + B square), so this option is not possible;

c. 1 8 (a+b) squared = 1 2 [1 4 (a2+b2)+1 2 ab] 1 2 ab, so this option is possible;

d, 1 4 ab 1 2 ab, so this option is possible

ab=ac, bac=80°, abc= acb=50°, pbc=10°, pcb=20°, bpc=150°, acp=30°, acp=30°, pcp=60°, pcp is an equilateral triangle, pp=pc, p ac= pac, p pc=60°, bpp =360°-150°-60°=150°, bpp = bpc, pbp pbc, pbp = pbc=10°, p bc=20°, abp = 30° and acp = 30°, abp = acp ,a, b, c, p four-point concentric, pac= p ac= p bc=20°, pab=60°

abc greater than 0 a+b+c=0 means that there are two negative numbers in a b c and a positive number and the absolute value of the positive number is greater than the absolute value of these two negative numbers, when the absolute value of a b c is greater than 1, the answer is a negative sign When the absolute value of a b c is less than or equal to 1, the answer is a negative sign.

So choose A

Question 1 a+b+c=0

These three numbers are divided into two cases.

All is 0, and the sum of any two numbers is the opposite of another number.

abc is greater than 0

There are two more cases.

All 3 numbers are positive numbers (0 is not included in the friendly reminder).

Two of the 3 numbers are negative and the other is positive.

Therefore, if we compare with the previous one and find that the previous one and the following are in conflict, then according to the two We can know that the value of a 1+b 1+c 1 must be 0 (you can take some special values to verify it at will).

Pick C and the second question is not very good.

Question 3: Just bring each one into it.

Solution: According to the topic: 2+m=5

2n+（6-m）=5

m=3n=1 msquared + n-squared.

3 sq + 1 sq.

10 [I'm glad to solve the above problems for you, I hope it will help you in your studies!] 】

From the five-time tetranomial m=3 from the same order to know 2n+6-m=5, bring in m to get 2n+6-3=5 so n=1

So the original formula = 25 + 1 = 26

9.Connecting AC, D+ E= EAC + DCA, (the sum of the common outer angles or the inner angles of the triangle is provable), so the sum of these five angles is 180 degrees (the sum of the inner angles of the triangle theorem).