Write a function to calculate volume of a tetrahedron.
import math
def volume_tetrahedron(num):
	volume = (num ** 3 / (6 * math.sqrt(2)))	
	return round(volume, 2)
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to calculate volume of a tetrahedron.
import math
def volume_tetrahedron(num):
	volume = (num ** 3 / (6 * math.sqrt(2)))	
	return round(volume, 2)[/INST]assert volume_tetrahedron(10)==117.85
assert volume_tetrahedron(15)==397.75
assert volume_tetrahedron(20)==942.81</s>