Hints About Logs
Date: 17 May 1995 06:01:50 -0400 From: Anonymous Subject: Logarithms. Dear Dr. Math, I just received your initial message the other day. I think this organization is great. Now you guys can help me out with my homework. Well my first question is: Do you know any hints on how to figure out logarithms? Possibly some secret little formulas the government's been hiding for years. Well anyway thanks a lot, and get back to me quick, my test is tommorow. Ara Donabedian High School Student at Augsburg American High School Augsburg, Germany
Date: 17 May 1995 11:04:46 -0400 From: Dr. Sydney Subject: Re: Logarithms. Dear Ara, Hello! I'm glad you wrote to us! It is usually a lot easier for us to help out with problems if you could tell us more specifically what kind of problems or concepts are troubling you. There are a lot of different kinds of problems you could do with logs, so I'm not sure exactly what you are having trouble with. There is no government secret about logs (to the best of my knowledge, that is, but I suppose you never really know... Hmmmmm...). I guess if you can remember the basic properties of logs, you should be fine. The important ones are: log a = x means b^x = a b log (ac) = (log a) + (log c) b b b log (a/c) = (log a) - (log c) b b b log a^r = r log a b b These are the main properties to keep in mind. If you have any specific questions, feel free to write back. Good luck on your test! --Sydney, "Dr. Math"
Date: 11/19/2001 at 00:56:52 From: Phyllis Stewart Subject: More Log Hints I have a few useful hints that you may want to add to your list: 1) If the base and the argument can be written as powers themselves, you can cancel like exponents or like bases. In the examples below the a's cancel: log (base x^a) y^a = log (base x) y log (base a^x) a^y = log (base x) y 2) Exchange the argument and the base and you get reciprocals: log (base x) y = 1/[log (base y) x] I give these tips to my students, as they are quite useful in some of the more difficult problems they encounter. Phyllis Stewart Naperville, IL
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