Right hand rule: Determining the direction of the Vector cross product

If you have a x b, as in the image to the right, you will place your right hand along the length ofb so that your fingers (except the thumb) can curve to point along a. In other words, you are sort of trying to make the angle theta between the palm and four fingers of your right hand. The thumb, in this case, will be sticking straight up (or out of the screen, if you try to do it up to the computer). Your knuckles will be roughly lined up with the starting point of the two vectors. Precision isn't essential, but I want you to get the idea since I don't have a picture of this to provide.

If, however, you are considering b x a, you will do the opposite. You will put your right hand along aand point your fingers along b. If trying to do this on the computer screen, you will find it impossible, so use your imagination. You will find that, in this case, your imaginative thumb is pointing into the computer screen. That is the direction of the resulting vector.

Vector X Vector = Vector