A wire can be enclosed into a square with a side length of 6.28 decimeters. What is the area of the circle

A wire can be enclosed into a square with a side length of 6.28 decimeters. What is the area of the circle

The radius of the circle is 6.28 × 4 ﹣ 3.14 ﹣ 2 = 4 decimeters
The area of the circle is 4 × 4 × 3.14 = 50.24 square decimeters

It is known that AB is a rational number and ab satisfies the formula 2A + 3b √ 5 = B + a √ 5 + 5 - √ 5

The key to solve this problem is to grasp that the rational part is the same as the irrational part. 2A = B + 53B = A-1

The application problems in Chapter 1 of mathematics 7,
More questions

The speed ratio of a and B is 4:5. After the first meeting, the speed of a increases by 1 / 4, the speed of B increases by 1 / 3, and the two cars return immediately after they arrive at BA. In this way, the second meeting point is 48km away from the first meeting point. How many kilometers is the distance between AB and a

For any integer a, the polynomial (a + 4) &# 178; - A & # 178;, can be divided by the largest integer

Polynomials (a + 4) ² - A & #178;
=（a+4+a）(a+4-a)
=4（2a+4）
=8(a+2);
Can be divided by 8
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Is the orbit of the moon the same as that of the earth around the sun?
If it is on the same plane, when the earth, the sun and the moon are in the same straight line, the earth is bigger than the moon, blocking all the sunlight, and the moon can't reflect light, how does the full moon appear?

Different, the ecliptic (the projection of the sun's orbit on the celestial sphere) and the white way (the projection of the moon's orbit on the ecliptic) have a difference of 5 degrees and 9 minutes. Therefore, when the moon is full, the moon is not in the shadow cone of the earth. If it is in the shadow cone, there will be an eclipse

What is plane stress state? What is plane strain stress state?

Due to the different stress conditions of members, the stress state of each point is also different
Unidirectional stress state: there is only one principal stress which is not equal to zero, such as the stress state of each point in the straight bar under axial tension and compression and pure bending
Two direction stress state (plane stress state): there are two principal stresses that are not equal to zero, such as the stress state of the twisted circular shaft and the points on the wall of the low pressure vessel
Three dimensional stress state: three principal stresses are not equal to zero, such as the stress state of each point in the wall of high pressure vessel

The perimeter of a square is a function of the area of a square. The perimeter is l and the area is s

Side length is L / 4, area is (L / 4) * (L / 4)
So the function is the square of S = (L / 4) ^ 2 (L / 4)

5 / 6 + 14 / 11, 5 / 6 - (4 / 9-1 / 3)
4 / 5-4 / 11 + 1 / 5-7 / 11 + 3 / 4 + 6 / 13 + 7 / 13-1 / 4
7:1 + 5:3 + 5:2 + 7:5 1-15:2-15:11-15:2

5/6+11/14=(35+33)/42=34/21
5/6-4/9-1/3=(15-8-6)/18=1/18
4/5-4/11+1/5-7/11=0
3/4+6/13+7/13-1/4=3/2
1/7+3/5+2/5+5/7=13/7
1-2/15-11/15-2/15=0

Given the function y = sin (2x - π / 6), find the range of function f (x) in the interval [- π / 12, π / 12]

When x ∈ [- π / 12, π / 12], (2x - π / 6) ∈ [- π / 3,0]
∴y=sin(2x-π/6)∈[-√3/2,0]
That is, the value range is [- √ 3 / 2,0]

A rectangle is 12 cm in width and 7 cm in width. If you subtract a square with a side length of 1 cm from each of its four corners, what is the perimeter of the remaining figure

The perimeter of the remaining figure is the same as that of the original rectangle
(12 + 7) × 2 = 38 (CM)