I don't have a special math education and when I study quaternions I spent a long time. Along the way, without realizing, I independently derived the Rodrigues equation, because now we know about the cross-production of vectors. I was very surprised that in all mathematical libraries instead of a complex product of quaternions under the name "quaternions" they use this simple and understandable equation.
But there is some misunderstanding...
This equation was derived by Rodriguez three years before Hamilton quaternions, BUT in this equation used vector cross-production, and as I later found out, they come from quaternions! This is a little confusing.
So what was invented first? Where am I going wrong?