Spreadsheets: logarithms: logs in other bases
The tutor shows the log() function on Excel and LibreOffice Calc.
Pretty much every scientific calculator has log and ln keys, with the log base 10, the ln base e. What if you need log base 5, for instance?
Of course, most people familiar with logs know the change of base trick
logpq = logq/logp (both logs now in base 10)
Therefore, log58 = log8/log5 = 1.2920…
Excel and LibreOffice Calc will evaluate the log in a base you specify. The function for both is
=log(number, base)
Therefore, if you enter
=log(216, 6)
you will receive the answer 3. (Of course, =log(8,5) will give 1.2920…:)
Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.
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