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Math formulas for logarithmic functions Author: Milos Petrovic ( www.mathportal.org ) Created Date: 8/7/2013 5:18:40 PM
Thinking of the quantity xm as a single term, the logarithmic form is log a x m = nm = mlog a x This is the second law. It states that when finding the logarithm of a power of a number, this can be evaluated by multiplying the logarithm of the number by that power. Key Point log a x m = mlog a x 7. The third law of logarithms As before ...
We use log as an abbreviation for the word logarithm. To find the value of a logarithm we need to solve an exponential equation. Example (a) The solution of 2x = 8 is x = 3. We can write this in logarithm notation as log 2 8 = 3 ‘log of 8 to base 2 is 3’ (b) x = 5 is the solution of 2x = 32. We can write this using logarithms as log 2
Firstly, the common logarithm, most commonly written as just log(x). In mathematics, we usually omit the base, and it is commonly understood to be base 10. The only exception to this rule is in computer science, where log(x) usually refers to log 2 (x). In short, log(x) = log 10 x
Simplify each of the following logarithmic expressions, giving the final answer as a single logarithm. a) log 7 log 22 2+ b) log 20 log 42 2− c) 3log 2 log 85 5+ d) 2log 8 5log 26 6− e) log 8 log 5 log 0.510 10 10+ − log 142, log 52, log 645, log 26, log 8010
log a b = c ,ac = b What does it mean? First of all the assumptions (restrictions) are important. The number a, called the base of the logarithm, has to be greater than 0 and cannot be equal to 1. The number b (which we take the logarithm of) has to be greater than 0. So the expressions like log 1 3, log p2 5 or log 4( 1) are not de ned in real
We can use logarithms to solve equations where the unknown is in the power as in, for example, 4x = 15. Whilst logarithms to any base can be used, it is common practice to use base 10, as these are readily available on your calculator. Solve the equation 4x = 15. We can solve this by taking logarithms of both sides. So,
