I don't think I quite followed the step where he/she writes "i^4 = 1", where they are relating rotation and the natural numbers. The RHS is theoretically the concept "identity under rotation". Why should it be be the same as the natural number 1?
Maybe I missed something in the explanation. Can somebody explain?
There is an implicit start from the unit vector 1. i (really 1 * i) is a 90° rotation of that. i^4 is four 90° rotations. Rotate anything four times and you've rotated it 360°, ending up where you started at 1.
Maybe I missed something in the explanation. Can somebody explain?