Trigonometry Helpers

trig-helpers.js

const {PI, asin, acos, atan} = Math;
/** 
Arcsine is an inverse of the sine function. 
In other words, it helps to find the angle of a triangle which has a 
know value of sine. As sine's codomain for real numbers is [−1, 1], 
we can only calculate arcsine for numbers in that interval.
*/

// Inverse sin, cos and tan fns in degrees.
const asinDeg = r => 180 * asin(r) / PI;
const acosDeg = r => 180 * acos(r) / PI;
const atanDeg = r => 180 * atan(r) / PI;