1, pigeon coop principle:

If we go to a wedding and there are more than 367 people, there must be the same person from Amanome (not in the same year).

This is the pigeon coop principle.

Put m things into n empty drawers at will (m >；; N), then there must be at least two things in a drawer.

Since there are 366 days in a year at most, at least two of these 367 people were born on the same day in the same month. This is equivalent to putting 367 things into 366 drawers, and at least two things are in the same drawer.

Application of pigeon hole principle in mathematics.

2, the area of the cat:

In winter, cats always hug their bodies together when they sleep, because this gives off the least heat.

In mathematics, an object with a certain volume and the smallest surface area is a sphere.

Shrinking the cat into a sphere can reduce the contact area with the outside world, reduce the speed of heat exchange, reduce the speed of heat loss, save energy and keep the body temperature.

Applied to the field of mathematics.

3. Four-leaf clover is called "Lucky Grass":

Clover, the scientific name of alfalfa, is a perennial herb with only three leaflets. The leaves are heart-shaped, and so are the darker parts of the leaves.

Four-leaf clover is produced by clover gene mutation, accounting for only one in 100 thousand. In other words, out of 100,000 alfalfa plants, you may only find one clover, because the probability is too small. Therefore, "four-leaf clover" is an internationally recognized symbol of luck.

Probability applied to mathematics.

4, the wheel is round rather than other shapes:

The center of the circle is called the center of the circle, and the distance from any point on the circle to the center of the circle is equal. Make the wheel round, and the axle is at the center of the circle. When the wheel rolls on the ground, the distance between the axle and the ground is always equal to the radius of the wheel.

So people sitting in the car can be pulled away smoothly by the car. If the wheel is deformed and not round, and the distance from the wheel to the axle is not equal, the car will not be stable again.

The knowledge about the center of the circle in mathematics is applied.

5. Fan blades are odd:

This is because odd blade combinations can bring more performance advantages than even blade combinations.

If the number of blades is even, forming a symmetrical arrangement, it is not only difficult to adjust the balance of the fan itself, but also easy to make the fan generate more * * * vibration at high speed, which leads to the fatigue caused by long-term * * * vibration, and finally leads to the occurrence of blade fracture and other situations.

Therefore, the design of axial flow fan is mostly asymmetric odd blade design.

The same design concept is also reflected in the design of daily electric fans or propeller helicopters. If the fan is a three-leaf structure, the blades are wider and the roots are stronger, and the density of each part needs to be uniform; If it is a five-leaf structure, the leaves are narrow and the thickness and strength are relatively low.

The concept of parity in applied mathematics.