When you are doing math, you might come up with a question: what’s the general direction of a cross product, you know, without boring calculation?
Well, we use the right hand law! It’s pretty much like the right hand law in electromagnetic or whatever, excuse my physics. Anyway, when happens, you can draw a graph like this:
And put your right hand parallel to the , like this:
Now make your hand into a fist. Fistify your hand!
And finally, the thumb direction is the general cross product direction! Yeah! That’s why when you do , you get the exact opposite direction.
This is just a reminder for myself.