What is the cross product of [1,2,1] and [3,1,-5] ?

1 Answer
Jan 2, 2016

[1,2,1] xx [3,1,-5] = [-11, 8, -5]

Explanation:

In general:

[a_x, a_y, a_z] xx [b_x, b_y, b_z]=[abs((a_y, a_z), (b_y, b_z)), abs((a_z, a_z), (b_z, b_x)), abs((a_x, a_y), (b_x, b_y))]

So:

[1,2,1] xx [3,1,-5]

= [abs((2, 1),(1,-5)), abs((1, 1), (-5, 3)), abs((1, 2),(3,1))]

= [(2*-5)-(1*1), (1*3)-(1*-5), (1*1)-(2*3)]

= [-10-1, 3+5, 1-6]

= [-11, 8, -5]