Why does the clock turn clockwise? What is the definition of clockwise and counterclockwise?

You really ask this question. First there is the rotation direction of the clock, then there are clockwise and counter clockwise directions. The fundamental problem is how to define the rotation direction of the clock. The left-handed spiral rule is used because the people who invented the clock lived in the northern hemisphere. In the early days, people only used the movement of shadows on the ground to time

Before the invention of the clock, how did people describe clockwise and counterclockwise?

There is a story in landscape architecture. The gardener moved the wisteria and wound it around the concrete column, but it was unprofessional. The wisteria felt very uncomfortable. When he got to the top of the shed, he immediately changed the direction of rotation
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Two sides of a triangle are 2 and 9, and the third side is odd

Let the length of the third side be X. according to the trilateral relation of the triangle, 9-2 ＜ x ＜ 2 + 9, that is, 7 ＜ x ＜ 11, ∵ x is odd, x = 9, and the perimeter of the triangle is 2 + 9 + 9 = 20

(2005 · Huai'an) if the lengths of two sides of a triangle are 2 and 9, and the perimeter is odd, then the triangles satisfying the condition have ()
A. 1 B. 2 C. 3 d. 4

Let the third side be x, then 7 ﹤ x ﹤ 11. ﹤ x = 8 or 9 or 10. The perimeter of a triangle is odd, so x = 8 or 10. There are two triangles satisfying the condition. So B is chosen

If the lengths of the two sides of the triangle are 2 and 7, then the value range of the third side length C is 0 When the perimeter is odd, the third side length is ．

According to the trilateral relation of a triangle, 7-2 ＜ C ＜ 7 + 2 is obtained, that is, 5 ＜ x ＜ 9. If ∵ the circumference is odd, then C is even, and the length of the third side is 6 or 8. Therefore, the answer is 5 ＜ C ＜ 9, 6 or 8

In △ ABC, the lengths of three sides are 5,12,2-3x, and the circumference is odd. Find the value of integer x and the maximum circumference
Note that 2-3x = 2 minus 3x

5,12,2-3X
Perimeter = 19-3x
1: 5 + 2-3x > 12.2-3x > 7.x5, which does not meet the requirements
So X1 = - 2, X2 = - 4, maximum circumference = 31

It is known that: in △ ABC, the lengths of three sides are 1-2x and 8 respectively, and the perimeter is even. Find the value of integer x and the maximum perimeter

The problem set is not complete, please give the complete problem set

In △ ABC, the lengths of three sides are 3,1-2a and 8 respectively, and the perimeter is even. Find the value of integer a and the maximum perimeter of △ ABC

From trilateral relations: 8-3

In the triangle ABC, ab = AC, the center line BD on the side of AC divides the circumference of the triangle into 21 cm and
In the triangle ABC, ab = AC, the center line BD on the side of AC divides the perimeter of the triangle into two parts, 21 cm and 12 cm. To find the length of the side BC, it is necessary to complete

1. If bad is 21: let AB = x, then AC = AB = x, ad = CD = x / 2 let BC = y have the following meaning: x + X / 2 = 21 (Note: Ba + ad = bad = 21) y + X / 2 = 12 (Note: BC + CD = BCD = 12) the solution is: x = 14y = 5, so BC is 52. If BCD is 21: let AB = x, then AC = AB = x, ad = CD = x / 2 let BC = y have the following meaning: x + X / 2 = 12

In △ ABC, ab = AC, the center line BD on AC divides the perimeter of the triangle into two parts of 24cm and 30cm, and calculates the three sides of the triangle

Let AB = AC = x for the waist of a triangle, if AB + ad = 24cm, then: x + 12x = 24  x = 16, the perimeter of the triangle is 24 + 30 = 54cm, so the three sides are 16, 16 and 22 respectively; if AB + ad = 30cm, then: x + 12x = 30  x = 20 ∵ the perimeter of the triangle is 24 + 30 = 54cm, and the three sides are 20, 20 and 14 respectively; therefore, the three sides of the triangle are 16, 16, 22 or 20, 20 and 14

Why does the clock turn clockwise? What is the definition of clockwise and counterclockwise?