Wednesday, 19 June 2013

algebra precalculus - Intuition behind logarithm change of base

I try to understand the actual intuition behind the logarithm properties and came across a post on this site that explains the multiplication and thereby also the division properties very nicely:





Suppose you have a table of powers of 2, which looks like this: (after revision)



01234567891012481632641282565121024



Each column says how many twos you have to multiply to get the number in that column. For example, if you multiply 5 twos, you get 22222=32, which is the number in column 5.




Now suppose you want to multiply two numbers from the bottom row, say 1664. Well, the 16 is the product of 4 twos, and the 64 is the product of 6 twos, so when you multiply them together you get a product of 10 twos, which is 1024.




I found that very helpful to understand the actual proofs for this property.



I still struggle to get the idea behind the change of base rule. I'm familiar with the proof that goes like:



logax=yay=x
logbay=logbx

ylogba=logbx
y=logbxlogba



But can somehow provide a explanation in the style of the quoted answer why this actually works?

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