Math.cos()

function getCircleX(radians, radius) {
  return Math.cos(radians) * radius;
}
console.log(getCircleX(1, 10));
// Expected output: 5.403023058681398
console.log(getCircleX(2, 10));
// Expected output: -4.161468365471424
console.log(getCircleX(Math.PI, 10));
// Expected output: -10

Math.cos(x)

Math.cos(-Infinity); // NaN
Math.cos(-0); // 1
Math.cos(0); // 1
Math.cos(1); // 0.5403023058681398
Math.cos(Math.PI); // -1
Math.cos(2 * Math.PI); // 1
Math.cos(Infinity); // NaN