find the area of a regular polygon inscribed in a circle in php

main.php
/**
 * Calculates the area of a regular polygon inscribed in a circle.
 *
 * @param int $n The number of sides of the polygon.
 * @param float $r The radius of the circle.
 * @return float The area of the polygon.
 */
function inscribedPolygonArea($n, $r) {
  $angle = pi() / $n; // The central angle of each triangle.
  $side = 2 * $r * sin($angle); // The length of each side of the polygon.
  $area = 0.5 * $n * $side * $r; // The area of the polygon.
  return $area;
}
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main.php
$area = inscribedPolygonArea(6, 5);
echo "The area of the hexagon is " . $area . ".";
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main.php
The area of the hexagon is 64.951905283832.
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