1. The problem statement, all variables and given/known data 2. Relevant equations I know the equations. See question below. 3. The attempt at a solution I am just wondering with this problem, how is it that they go from that derivative to the magnitude at the bottom of that image? I know the formula, but what I mean is they have no steps for something that to me seems extremely tedious, so I'm assuming they are applying some type of identity to save time and trouble, but I'm not seeing it? If someone can show me an easier way than squaring each of those, splitting it all up, factoring, then trying to make it so you can take the square root of it all, I'd really appreciate it.