log base c++

To calculate the logarithm base in C++, you can use the log() function from the cmath library. Here's an example:

#include <iostream>
#include <cmath>

int main() {
    double number = 100;
    double base = 10;
    double result = log(number) / log(base);

    std::cout << "Logarithm base " << base << " of " << number << " is: " << result << std::endl;

    return 0;
}

In this example, we declare a double variable "number" and assign it a value of 100. We also declare a double variable "base" and assign it a value of 10. Then, we calculate the logarithm base "base" of "number" using the log() function. The result is obtained by dividing the natural logarithm (log()) of "number" by the natural logarithm of "base". Finally, we print the result using cout.

Note that the log() function in C++ returns the natural logarithm (base e) of a number. To calculate logarithms with different bases, you need to use the base change formula, which involves taking the natural logarithm of the number and dividing it by the natural logarithm of the desired base.