Multiplication of quaternions (chapter 3)

[jcremona]

I really appreciate this book, great work!
In Section 3.4.1 Quaternion Operations, multiplication between two quaternions is defined. A more concise form is presented. According to the text, this form uses inner and outer product. In my opinion, this is a mistake. It is not the outer product but the cross product. Outer product is a vector operation whose result is a matrix. On the other hand, Cross product gives a vector as a result (null vector when both vectors are parallel).
https://en.wikipedia.org/wiki/Cross_product

[gaoxiang12]

Thanks @jremona, I'll correct it in a few days.

[jcremona]

Hhmm, actually, after reading the chapter again, I realized that this operation is presented as "Outer product" in the whole chapter. Thanks for your reply.