1 from math import *

     2 

     3 def dot(a,b):

     4 	sum = 0

     5 	for i in range(min(len(a),len(b))):

     6 		sum += a[i]*b[i]

     7 	return sum

     8 

     9 def cross(a,b):

    10 	return (

    11 		a[1]*b[2] - a[2]*b[1],

    12 		a[2]*b[0] - a[0]*b[2],

    13 		a[0]*b[1] - a[1]*b[0]

    14 	)

    15 

    16 def unit(a):

    17 	m = mag(a)

    18 	return (a[0]/m, a[1]/m, a[2]/m)

    19 

    20 def mag(a):

    21 	return sqrt(mag2(a))

    22 

    23 def mag2(a):

    24 	return a[0]*a[0] + a[1]*a[1] + a[2]*a[2]