In preparing to teach my son to drive I was looking for a visual for mirror adjustment. MOST drivers have their mirrors adjusted WRONG and don't even know it. So I thought I would pin this. You should NOT be able to see your own car in your mirror.
Safety mirrors are useful for all kinds of things. Put a mirror near a mineral feeder and the animals eat more mineral, use one to provide "company for a sick animal at a vet hospital or in isolation, put one in a trailer when taking animals solo!