Added RadianToDegree.js and RadianToDegree.test.js in Maths directory

Maths/RadianToDegree.js

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+/*
+ * Radian : https://en.wikipedia.org/wiki/Radian
+ * Degree : https://en.wikipedia.org/wiki/Degree_(angle)
+ *
+ * Angle in Degree = ( Angle in Radian ) x ( 180 / pi )
+ *
+ * Example :
+ * Question : Convert pi / 2 degree to radian
+ * So, Angle in Radian = pi / 2
+ *
+ * Solution :
+ * Angle in Degree = ( pi / 2 ) x ( 180 / pi ) = 90
+ *
+ * So, pi / 2 radian is equal to 90 degree
+ */
+
+/**
+ * @param {number} radian
+ * @return {number}
+ */
+export const radianToDegree = (radian) => {
+  return radian * (180 / Math.PI)
+}

Maths/test/RadianToDegree.test.js

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+import { radianToDegree } from '../RadianToDegree'
+
+test('should convert radian to degree:', () => {
+  const degreeEqual = radianToDegree(0)
+  expect(degreeEqual).toBe(0)
+})
+
+test('should convert radian to degree:', () => {
+  const degreeEqual = radianToDegree(Math.PI / 4)
+  expect(degreeEqual).toBe(45)
+})
+
+test('should convert radian to degree:', () => {
+  const degreeEqual = radianToDegree(Math.PI / 2)
+  expect(degreeEqual).toBe(90)
+})
+
+test('should convert radian to degree:', () => {
+  const degreeEqual = radianToDegree(Math.PI)
+  expect(degreeEqual).toBe(180)
+})