How do you calculate log65 with a calculator?

1 Answer
Aug 12, 2016

log65=log5log60.8982444

Explanation:

Use the change of base formula:

logab=logcblogca

So you can use natural or common logs:

log65=ln5ln6

log65=log5log6

In fact, if you know log20.30103 and log30.47712 then you can get a reasonable approximation with basic arithmetic operations:

log65=log5log6=log10log2log2+log3

10.301030.30103+0.47712=0.698970.778150.89825

Actually the true value is closer to 0.8982444