﻿ Sydney代写essay：角度

# Sydney代写essay：角度

#### 2017-02-01 14:55 Sydney代写essay：角度度是最常用的角度测量单位之一，虽然它不是一个SI单位（国际单位制）。一个完整的旋转定义为360度，所以度等于1／360的全旋转，由1O。它已经被使用了数千年。有几种理论来解释为什么选择360而不是其他数字。一种理论是古代天文学家注意到地球围绕太阳公转大约需要360天。因此，他们使用360天为一年，这意味着地球围绕太阳旋转的角度在一天是一个程度。另一个说法是，360号有许多因子，使它容易界定相关概念。例如，数字360可以除以数字24，这意味着世界可以划分为24个时区。

Sydney代写essay：角度

Degree is one of the most commonly used units for angle measure, though it’s not an SI unit (International System of Units). A full rotation is defined as 360 degrees, so a degree is equal to 1/360 of a full rotation, represented by 1o. It has been used for thousands of years. There are several theories to explain why choosing 360 rather than other numbers. One theory is that ancient astronomers noticed that one revolution of the earth around the sun takes about 360 days. Thus, they use 360 days for a year, which means the angle of the earth rotating around the sun in one day is one degree. Another theory is that the number 360 has many divisors, making it easy to defining some other concepts. For example, the number 360 can be divided by the number 24, which means that the world can be divided into 24 time zones.

For many practical purposes, a degree is not small enough, as the latitude and longitude on the Earth. When this case happens, one degree must be subdivided. Similar to the clock, one degree can be divided into 60 minutes, and one minute can be divided into 60 seconds. For example, 30 degrees 20 minutes 40 seconds can be abbreviated as 30o2040’’. If the precision is still not enough, the seconds can be represented by floating point, such as 30o2040.124’’.

Angles can be classified by their degrees. An angle that is less than 90o is called acute angle; an angle that is equal to 90o is called acute angle; an angle that is greater than 90o is called obtuse angle. Specifically, when the angle is equal to 0o or 180o, the two rays are collinear. In Figure 2, (a) is an acute angle, (b) is a right angle, (c) is an obtuse angle.