I would like to expand a tensor expression of 3-d vectors. However, the code runs really slow, the problem is asked here: Why is TensorExpand so slow for vector operations?

However, I found that by assuming the 3-d vectors as real numbers, the code could be faster. For example, to expand $(a-b)\times c.d$:

$Assumptions = (a | b | c | d) \[Element] Reals;
TensorExpand[( a - b)\[Cross]c.d]

Instead of using $Assumptions = (a | b | c | d) \Vectors[3] I used Reals. It was really faster, except that the result was not perfect:

$$ a\times c.d+b (-1)\times c.d$$

I got a -1 here, which should be b.

Can we have some operations that could put the "b" in the correct place?



Your Answer

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