How to evaluate logarithms in Maxima?

问题

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).

回答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

回答2:

or use float :

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

gives:

2.999999999999999

来源：https://stackoverflow.com/questions/36271504/how-to-evaluate-logarithms-in-maxima