Mathf.Sqrt  

print(Mathf.Sqrt(10));

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        print(Mathf.Sqrt(10));
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        print(Mathf.Sqrt(10))