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scribu
Asked: 2012-09-23 16:11:48 +0800 CST

Syntax for specifying base of logarithm in Calculator

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In the Programming mode of gcalctool, you have a log button, which calculates the logarithm, but how do I know what base it's using and how do I change it?

For example, how would I calculate the base 2 logarithm for 16?

calculator

3 Answers

  1. Best Answer

    By default the log button calculates base-10 logarithms (while the "ln" button does, of course, base-e logarithms).

    To specify a different base, you use a "subscript":

    • Type "log" in the input field.
    • Input your desired base with a subscript. This can be done either by clicking on the "downarrow-n" button (top left) and then entering the number, or by pressing Alt while typing the number.
    • Finally type the number whose logarithm you want to calculate.

    By the way, I found this pretty easily by accessing gcalctool's help (press F1) and looking for logarithms in the index.

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  2. You can also use the base change formula: 

    ln(1024)/ln(2) = log (base 2) (1024)
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  3. You may use this frequently and like a button instead of writing out the base change formula again and again. Add within gcalculator (kde) by selecting:

    edit preferences functions Name: log2 Variable: x Expression: log(x)/log(2) add update close view buttons functions

    now to get log2(1024): type 1024 into the calculator and PRESS ENTER hit the 'fun' button select log2 the answer is 10

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