How to evaluate logarithms in Maxima?

Question

Following examples from here, and here I tried this:

log2(x) := log(x) / log(2);
log2(8), float;

But this doesn't give 3, instead I get log(8)/log(2).

Answer 1

You have to simplify radicals:

(%i1) log2(x) := log(x) / log(2);
                                          log(x)
(%o1)                          log2(x) := ------
                                          log(2)
(%i2) radcan(log2(8));
(%o2) 

                             3

Answer 2

or use float :

float(log(8)/log(2));

gives:

2.999999999999999

Answer 3

Another way to calculate logarithms in base 10:

You can also write in the command line: load(log10);(enter)

Then for the calculation of the decimal logarithm: log10(100);(Enter) the result is 2, and so on. To exemplify I did some calculations with log10. These results are shown in the picture below