Creating a log function with a custom base

Question

I have a formula and this formula uses a log function with a custom base for example log with a base of b and value of x. In objective-c, I know there are log functions that calculate without a base and base of either 2 or 10.

Is there a function that has the ability to calculate a log function with a custom/variable base? or maybe there is an alternative method of completing this formula.

The basic idea of my formula is this log(1+0.02)(1.26825) (1+0.02 is the base). This should equal 12.000.

Answer 1

Like this:

double logWithBase(double base, double x) {
    return log(x) / log(base);
}