2
$\begingroup$

Suppose I want to calculate:

Cross[A1 + B1, A2 - B2] + Cross[A1 - B1, A2 + B2]

which is equal to 2 A1xA2 - 2 B1xB2

Using FullSimpify won't do it. I can use Distribute

Distribute[Cross[A1 + B1, A2 - B2]] + Distribute[Cross[A1 - B1, A2 + B2]]
(* which gives: 2 A1xA2 + A1x(-B2) + A1xB2 + (-B1)xA2 + (-B1)xB2 + B1xA2 + B1x(-B2) *)

Close but it still keeps the - into parentheses, keeping terms that cancel each other. How can I overcome this?

Improve this question
$\endgroup$
2
  • 1
    $\begingroup$ TensorExpand[Cross[A1+B1,A2-B2]+Cross[A1-B1,A2+B2]] $\endgroup$
    – chyanog
    Commented Apr 11, 2021 at 9:58
  • $\begingroup$ Please post it as an answer. I wasn't aware of TensorExpand, thanks $\endgroup$
    – geom
    Commented Apr 11, 2021 at 10:05

1 Answer 1

Reset to default
5
$\begingroup$

TensorExpand[Cross[A1+B1,A2-B2]+Cross[A1-B1,A2+B2]] gives

2 A1×A2 - 2 B1×B2

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.