

It sounds like your driving instructor wasn’t any good. A good driving instructor will never put you in a situation that you are not ready for. They never should have allowed you to get a licence until you felt safe.
If you feel like you’re not in control then you’re right - this accident is proof of that. If you want to try driving again, I highly recommend getting a good driving instructor first - one who won’t put you in situations you can’t handle.
If you can get everywhere you need to without driving, then you can save yourself a lot of money by not paying for a car, insurance, or registration.
You always have the right to say no, and you can always say “not now”. Maybe wait a few more weeks before making a decision.
If you’re trying to calculate it, then it’s quite difficult.
If you just want to use it in a computer program, most programming languages have it as a constant you can request. You get to pick whether you want single or double precision, but both are atomic (a single instruction) on modern computers.