Mathf.PI 圆周率

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
	public float radius = 5;
	void Start() {
		float perimeter = 2 * Mathf.PI * radius;
		Debug.Log("The perimeter of the circle is: " + perimeter);
	}
}

var radius : float = 5;

function Start() {
	var perimeter : float = 2 * Mathf.PI * radius;
	Debug.Log("The perimeter of the circle is: " + perimeter);
}