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Solution 3.3:6c

From Förberedande kurs i matematik 1

Revision as of 09:49, 26 September 2008 by Ian (Talk | contribs)
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Before we even start thinking about transforming log2 and log3 to ln, we use the log laws


lgab=blga


lgab=lga+lgb 


to simplify the expression


log3log23118=log3118log23=log3118+log3log23 


With help of the relation


2log2x=x and 3log3x=x


and taking the natural logarithm , we can express log2 and log3 using ln,


log2x=lnxln2 and log3x=lnxln3


The two terms log3 118 and log3 log2 3 can therefore be written as


log3118=ln3ln118 and log3log23=log3ln2ln3 


where we can simplify the last expression further with the logarithm law, log a/b = log a – log b, and then transform log3 to ln,


log3ln2ln3=log3ln3log3ln2=ln3lnln3ln3ln2 


In all, we thus obtain


log3log23118=ln3ln118+ln3lnln3ln3ln2


Input into the calculator gives


log3log231184762


NOTE: the button sequence on a calculator will be:


118LN3LN+3LNLN3LN2LNLN3LN=