Raians and Degrees (弧度和度数)

Radians are another way to measure angles. Sometimes radians will be used in questions, and other times you may choose to use them since they are sometimes more convenient than degrees.

弧度是另一种度量角度的方法。有时候弧度是一种更便捷的表示方法相比度数。

 

A degree is equal to ¹ /₃₆₀ of a circle, while a radian is equal to the angle that intercepts an arc of the same length as the radius of the circle. In the figure below, arc AB has length r , and the central angle measures one radian.
一度数等于圆的1/360，一弧度表现为半径长度的圆弧所对应的角度。如下图所示，弧形AB的长度为半径r,它所对的中央的角所测量出的弧即为1弧度

When converting between the two measurement systems, use the proportion:
当在两个测量系统之间转换时，可以使用下面的比例：

 

which can be simplified to:
可以简化成：

 

To convert from degrees to radians:

 从度数转化成弧度：

multiply the degree measure by ^π /₁₈₀ . For example, 60º is eual to ^60π / ₁₈₀ = ^π /₃ radians.

 度数去乘以^π /_180， 例 60度:  60 * ^π /180 = ^π /₃ 弧度

To convert from radians to degrees:

 从弧度转化为度数：

multiply the measure in radians by ¹⁸⁰ /_π . For example, ^π /₄ radians is equal to ^180π / _4π = 45º.

 弧度乘以¹⁸⁰ /_π, 例^π /₄ 弧度：^180π / _4π = 45º.

Here are the most important angle measures in degrees and radians:
下面是比较重要的常用度的转换：

On the Math IC, it is sometimes a better idea to work solely in radians, rather than convert back and forth between radians and degrees. Using radians is especially easy on graphing calculators that allow you to switch into radian mode.
在数学上，单独使用弧度来计算比弧度与度数之间来回转换更好一些。但是弧度特别是在图形计算方面更容易。
（随便翻译的，见笑了，呵呵）