如何使用度数而不是弧度来获得sin，cos和tan？

When I'm working with math in JS I would like its trig functions to use degree values instead of radian values. How would I do that?

当我在JS中使用数学时，我希望它的trig函数使用度数值而不是弧度值。我该怎么办？

5 个解决方案

#1

160

You can use a function like this to do the conversion:

您可以使用这样的函数进行转换：

function toDegrees (angle) {
  return angle * (180 / Math.PI);
}

Note that functions like sin, cos, and so on do not return angles, they take angles as input. It seems to me that it would be more useful to you to have a function that converts a degree input to radians, like this:

请注意，像sin，cos等函数不返回角度，它们将角度视为输入。在我看来，拥有一个将度数输入转换为弧度的函数会更有用，如下所示：

function toRadians (angle) {
  return angle * (Math.PI / 180);
}

which you could use to do something like tan(toRadians(45)).

你可以用来做tan之类的东西（toRadians（45））。

#2

Multiply the result by 180/Math.PI to convert from radians to degrees.

将结果乘以180 / Math.PI，将弧度转换为度数。

You could also define your own functions:

您还可以定义自己的功能：

function sinDegrees(angle) {return Math.sin(angle/180*Math.PI);};

and so on.

等等。

#3

I created my own little lazy Math-Object for degree (MathD), hope it helps:

我为学位（MathD）创建了自己的小懒惰Math-Object，希望它有所帮助：

//helper
/**
 * converts degree to radians
 * @param degree
 * @returns {number}
 */
var toRadians = function (degree) {
    return degree * (Math.PI / 180);
};

/**
 * Converts radian to degree
 * @param radians
 * @returns {number}
 */
var toDegree = function (radians) {
    return radians * (180 / Math.PI);
}

/**
 * Rounds a number mathematical correct to the number of decimals
 * @param number
 * @param decimals (optional, default: 5)
 * @returns {number}
 */
var roundNumber = function(number, decimals) {
    decimals = decimals || 5;
    return Math.round(number * Math.pow(10, decimals)) / Math.pow(10, decimals);
}
//the object
var MathD = {
    sin: function(number){
        return roundNumber(Math.sin(toRadians(number)));
    },
    cos: function(number){
        return roundNumber(Math.cos(toRadians(number)));
    },
    tan: function(number){
        return roundNumber(Math.tan(toRadians(number)));
    },
    asin: function(number){
        return roundNumber(toDegree(Math.asin(number)));
    },
    acos: function(number){
       return roundNumber(toDegree(Math.acos(number)));
   },
   atan: function(number){
       return roundNumber(toDegree(Math.atan(number)));
   }
};

#4

Create your own conversion function that applies the needed math, and invoke those instead. http://en.wikipedia.org/wiki/Radian#Conversion_between_radians_and_degrees

创建自己的转换函数，应用所需的数学，然后调用它们。 http://en.wikipedia.org/wiki/Radian#Conversion_between_radians_and_degrees

#5

I like a more general functional approach:

我喜欢更通用的功能方法：

/**
* converts a trig function taking radians to degrees
* @param {function} trigFunc - eg. Math.cos, Math.sin, etc.
* @param {number} angle - in degrees
* @returns {number}
*/
const dTrig = (trigFunc, angle) => trigFunc(angle * Math.PI / 180);

or,

要么，

function dTrig(trigFunc, angle) {
  return trigFunc(angle * Math.PI / 180);
}

which can be used with any radian-taking function:

可以与任何弧度函数一起使用：

dTrig(Math.sin, 90);
  // -> 1

dTrig(Math.tan, 180);
  // -> 0

Hope this helps!

希望这可以帮助！

#1

160