300 to 500 words fast

300 to 500 words fast

On the floor or wall paved with ceramic tiles, the adjacent floor tiles or ceramic tiles are flat and close together, and there is no gap on the whole floor or wall
For example, triangles. Triangles are planar figures composed of three line segments which are not on the same line. Through experiments and research, we know that the sum of the internal angles of triangles is 180 degrees, and the sum of the external angles is 360 degrees. Six regular triangles can cover the ground
Let's look at the regular quadrilateral. It can be divided into two triangles. The sum of the internal angles is 360 degrees. The degree of an internal angle is 90 degrees and the sum of the external angles is 360 degrees
What about a Pentagon? It can be divided into three triangles. The sum of the internal angles is 540 degrees. The degree of an internal angle is 108 degrees, and the sum of the external angles is 360 degrees. It can't cover the ground
Hexagon, it can be divided into four triangles, the sum of internal angles is 720 degrees, the degree of an internal angle is 120 degrees, and the sum of external angles is 360 degrees
It can be divided into five triangles, the sum of the inner angles is 900 degrees, the degree of an inner angle is 900 / 7 degrees, and the sum of the outer angles is 360 degrees
From this, we get that. N-polygon can be divided into (n-2) triangles, the sum of internal angles is (n-2) * 180 degrees, the degree of an internal angle is (n-2) * 180 ／ 2 degrees, and the sum of external angles is 360 degrees. If (n-2) * 180 ／ 2 can divide 360, then it can be used to cover the ground, if not, it cannot be used to cover the ground
We can not only use one regular polygon to cover the ground, but also use two, three and more graphics to cover the ground
For example: regular triangle and square, regular triangle and hexagon, square and regular octagon, regular pentagon and regular octagon, regular triangle and square and regular hexagon
In real life, we have seen a variety of patterns made of regular polygons. In fact, many patterns are often made of irregular basic graphics

Summary of mathematics semester in grade one

Do you have 350 words to reflect on and summarize the midterm mathematics examination in grade one
I got a full mark in the exam. I want to write something about how to do it. In the future, I will try my best to praise the teacher. I don't want an outline. If I write well, I will add something

1、 The acceptance of new knowledge and the cultivation of mathematical ability are mainly carried out in class. Therefore, we should pay special attention to the learning efficiency in class and seek the correct learning methods. In class, we should closely follow the teacher's ideas, actively carry out the thinking, predict the following steps, and compare our problem-solving ideas with what the teacher has

Can t be eliminated from the expressions v = V0 + at and x = v0t + 1 / 2at, so that the relationship between displacement X and velocity V can be obtained directly?

V = V0 + at x = v0t + 1 / 2at can only get x = (V ^ 2-v0 ^ 2) / 2A

In the space rectangular coordinate system, how to find the equation of a plane?

If we know a point M0 (x0, Y0, Z0) on the plane and the normal vector n (a, B, c) of the plane, we can establish the equation of the plane. If any point m (x, y, z) on the plane, the vector m0m is perpendicular to the vector n, and the scalar product of the two vectors is zero

What is the change of the volume of water ice? What is the harm of this phenomenon

Because the density of water is 1g / cm3, and the density of ice is about 0.9g/cm3, after a certain mass of water solidifies into ice, its volume will be increased to 10 / 9 (about 1.11 times) of the original because the mass remains unchanged and the density decreases

On the formula of pulley block
I remember the pulley block lifted vertically w = GH w = FNH
But the one lying down forgot

W = FL
Wtotal = FS = NFL
f: In the face of the friction of goods
F: Hand pull
S: The length of the rope pulled by hand
n: The number of strands of rope connected to the movable pulley
50: Distance of goods
Unknown can be questioned

ln（e-3x+1）-ln（e3x+1）=ln( e−3x+1 e3x+1 )=lne-3x
How is this formula derived?

How to calculate the date in geographical time zone?
For example, now Beijing is the eighth East District, 9:00 on March 3rd, so what's the time of the third west district?
And Beijing is the East eight district, 22:00 on March 3, so what's the West ten district?
I just don't understand
My answer is west three. It's 21:00 on March 2nd
It's 4:00 on March 4th in West 10, right?

The world is divided into 24 time zones. They are central time zone (zero time zone), East 1-12 zone, West 1-12 zone. Each time zone spans longitude 15 degrees, and the time is exactly one hour. The last East and West 12 zones span longitude 7.5 degrees, and the East and West longitudes are 180 degrees. The time on the central longitude of each time zone is uniformly adopted in this time zone

Natural numbers (except 0) can be divided into (), () and ()

Natural numbers (except 0) can be divided into (1), (prime) and (composite) according to the number of factors