feat: add polygon inside circle solution

Author: marcode24

codewars/polygon-inside-circle/README.md

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+# Calculate the Area of a Regular n Sides Polygon Inside a Circle of Radius r
+
+## Description
+
+Write the following function:
+
+```js
+function areaOfPolygonInsideCircle(circleRadius, numberOfSides)
+```
+
+It should calculate the area of a regular polygon of `numberOfSides`, `number-of-sides`, or `number_of_sides` sides inside a circle of radius `circleRadius`, `circle-radius`, or `circle_radius` which passes through all the vertices of the polygon (such circle is called **circumscribed** circle or **circumcircle**). The answer should be a number rounded to 3 decimal places.
+
+Input :: Output Examples
+
+```js
+areaOfPolygonInsideCircle(3, 3); // returns 11.691
+
+areaOfPolygonInsideCircle(5.8, 7); // returns 92.053
+
+areaOfPolygonInsideCircle(4, 5); // returns 38.042
+```
+
+**Note:** if you need to use Pi in your code, use the native value of your language unless stated otherwise.

codewars/polygon-inside-circle/solution.js

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+const areaOfPolygonInsideCircle = (cRadius, nSides) => {
+  const angle = (180 * (nSides - 2)) / nSides / 2;
+  const apotema = cRadius * Math.sin(Math.PI * (angle / 180));
+  const side = cRadius * Math.cos(Math.PI * (angle / 180)) * 2;
+  const area = (nSides * side * apotema) / 2;
+  return Number(area.toFixed(3));
+};
+
+module.exports = areaOfPolygonInsideCircle;

codewars/polygon-inside-circle/solution.test.js

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+const areaOfPolygonInsideCircle = require('./solution');
+
+describe('Area of polygon inside circle', () => {
+  const testCases = [
+    {
+      input: [5.8, 7],
+      output: 92.053,
+    },
+    {
+      input: [3, 3],
+      output: 11.691,
+    },
+    {
+      input: [4, 5],
+      output: 38.042,
+    },
+    {
+      input: [2, 4],
+      output: 8,
+    },
+    {
+      input: [2.5, 5],
+      output: 14.86,
+    },
+  ];
+
+  it('should return a number type', () => {
+    expect(typeof areaOfPolygonInsideCircle(5.8, 7)).toBe('number');
+  });
+
+  it.each(testCases)('should return the correct output', ({ input, output }) => {
+    expect(areaOfPolygonInsideCircle(...input)).toBe(output);
+  });
+});