6760, Math 21a, Fall 2009
Exhibits page Math 21a 2009, Multivariable Calculus
Triple Cross product
Course head: Oliver Knill
Office: SciCtr 434

Triple cross product

In a homework problem, you had to verify the identity
a x (b x c) =  (a.c)b - (a.b) c
Here is how you could verify that fast with Mathematica
u = {u1, u2, u3}; v = {v1, v2, v3}; w = {w1, w2, w3};
Simplify[ Cross[u, Cross[v, w]] ==  (u.w) v - (u.v) w ]
You can not throw this into wolfram alpha yet to get an answer, but if you copy paste that into Mathematica you should get an answer. You do not have to remember the above identity.

Questions and comments to knill@math.harvard.edu
Math21b | Math 21a | Fall 2009 | Department of Mathematics | Faculty of Art and Sciences | Harvard University