I will again caution you in trying to use mathematical formulas as a defense for speeding. Most of the time, the judge will just point his/her nose up the air and not even pay attention to the numbers you present. Even if the officer made up a number, the judge will still conclude that if you were not going 50, then maybe you were going 45, and thats still speeding, and you'll still get hit with a fine (and points on your driving record). I write this because I had it happen to me - I challenged a ticket because I thought I had an easy case - the officer's testimony said he turned on his radar from the opposing lane of traffic, 25 feet from my car. That would certainly not have been enough time to lock on (I would have gone by him in a fraction of a second, even at the limit). So I presented my calculations, and even presented evidence that the road was not marked with speed limit signs. Judge concluded I was using "approximations to discredit the officer and confuse the court." You can guess the outcome from there.
Its best to try to settle the case before it gets to court, by either using a traffic school option (usually you can go to traffic once to get it removed from your record), or having an attorney amend your ticket to a non moving violation (aka tail lights were out, or something similar) for a fee. In either case you'll pay a fine, but most importantly it won't go on your driving record.