In this C++ tutorial, you will learn how to find the natural logarithm of given number using log() function of cmath, with syntax and examples.
C++ log()
C++ log() returns natural logarithm of given number. It computes the logarithm of given value to base-e.
Syntax
The syntax of C++ log() is
log(x)
where
| Parameter | Description |
|---|---|
| x | A double, float, long double, or integral type value. The value of x must be in the range [0, inf]. |
Returns
The return value depends on the type of value passed for parameter x. The return value of log(x) is
- double if x is double or integral type.
- float if x is float.
- long double if x is long double.
The synopsis of log() function is
double log (double x); float log (float x); long double log (long double x); double log (T x);// for integral type argument values
log() is a function of cmath library. Include cmath library at the start of program, if using log() function.
Example
In this example, we read a value from user into variable x, and find its logarithm value using log().
C++ Program
#include <iostream>
#include<cmath>
using namespace std;
int main() {
double x;
cout << "Enter a number : ";
cin >> x;
double result = log(x);
cout << "log(" << x << ") : " << result << endl;
} Output
Enter a number : 1 log(1) : 0 Program ended with exit code: 0
Enter a number : 5 log(5) : 1.60944 Program ended with exit code: 0
Enter a number : -2 log(-2) : nan Program ended with exit code: 0
Conclusion
In this C++ Tutorial, we learned the syntax of C++ log(), and how to use this function to find the natural logarithm of given number, with the help of examples.