CODEWITHSUNDEEP
javascriptmath
David G
David G

Reputation: 96810

How can I get sin, cos, and tan to use degrees instead of radians?

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?

Upvotes: 139

Views: 166902

Answers (5)

Benjamin Atkin
Benjamin Atkin

Reputation: 14725

There's a project with more than a thousand stars on GitHub that provides functions for converting from degrees to radians and radians to degrees.

To install:

npm i @stdlib/math

To import:

const rad2deg = require('@stdlib/math/base/special/rad2deg')
const deg2rad require('@stdlib/math/base/special/deg2rad')

To use:

console.log(Math.sin(deg2rad(90)))
console.log(rad2deg(Math.asin(1)))

Upvotes: 2

Niet the Dark Absol
Niet the Dark Absol

Reputation: 324640

Multiply the input by Math.PI/180 to convert from degrees to radians before calling the system trig functions.

You could also define your own functions:

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

and so on.

Upvotes: 42

David Nishikawa
David Nishikawa

Reputation: 61

I like a more general functional approach:

/**
* 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,

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

which can be used with any radian-taking function:

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

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

Hope this helps!

Upvotes: 6

Daniel Budick
Daniel Budick

Reputation: 1850

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

//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)));
   }
};

Upvotes: 14

Peter Olson
Peter Olson

Reputation: 142921

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

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:

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

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

Upvotes: 278

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