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**Mockarutan** Hi! I'm new here and I'm not sure this is the right sub-forum...

But anyway, I'm learning about quaternions, and reading the book John Vince - Quaternions for Computer Graphics. And he is proving that the quaternion notation q = [s, v], have the same "algebraic" rules as the other ways of representing quaternions.

And now he is proving that i*j = k, j*k = i, k*i = j, in that notation, so here is how it goes:

ij = [0, i][0, j]

= [-i * j, i×j]

= [0,k]

I get that i×j = k, but -i*j = 0?

How does that work? I have searched for this and it's not mentioned anywhere?

Thanks in advance!