vector u = 1 -2 3 -4
vector v = 6 7 1 -2
vector w = 5 -4 5 7
vector u * v = 3
vector u * w = 0
vector v * w = -7
factorial 0 = 1
factorial 1 = 1
factorial 2 = 2
factorial 3 = 6
factorial 4 = 24
factorial 5 = 120
factorial 6 = 720
my_cos 0 = 1.000000
   cos 0 = 1.000000
my_cos 10 = 0.984808
   cos 10 = 0.984808
my_cos 20 = 0.939693
   cos 20 = 0.939693
my_cos 30 = 0.866025
   cos 30 = 0.866025
my_cos 40 = 0.766044
   cos 40 = 0.766044
my_cos 50 = 0.642788
   cos 50 = 0.642788
my_cos 60 = 0.500000
   cos 60 = 0.500000
my_cos 70 = 0.342020
   cos 70 = 0.342020
my_cos 80 = 0.173648
   cos 80 = 0.173648
end