C++ Math log
The function is used to find the natural logarithm (base-e logarithm) of a given number.
Mathematically:
Suppose 'x' is a given number:
logex = log(x);
Syntax
float log(float x);
double log(double x);
long double log(long double x);
double log(integral x);
Parameter
x : It is the value whose natural logarithm is to be calculated.
Return value
Following are the return values of a given number:
| Parameter(x) | Return value |
|---|---|
x>1 |
Positive |
x=1 |
0 |
| 1>x>0 | Negative |
x=0 |
-infinty |
x<0 |
Not a Number(nan) |
Example 1
Let's see a simple example when the value of x is 1.
#include <iostream>
#include<math.h>
using namespace std;
int main()
{
int x=1;
std::cout << "Value of x is : " <<x <<std::endl;
cout<<"Log value of x is : "<<log(x);
return 0;
}
Output:
Value of x is : 1
Log value of x is : 0
In this example, the value of x is 1. Therefore, the function log returns the positive value i.e 0.
Example 2
Let's see another simple example
#include <iostream>
#include<math.h>
using namespace std;
int main()
{
int x=3;
std::cout << "Value of x is : " <<x <<std::endl;
cout<<"Log value of x is : "<<log(x);
return 0;
}
Output:
Value of x is : 3
Log value of x is : 1.09861
In this example, the value of x is 3. Therefore, the function log returns the positive value i.e 1.09861
Example 3
Let's see a simple example when the value of x is -0.5.
#include <iostream>
#include<math.h>
using namespace std;
int main()
{
float x= -0.5;
std::cout << "Value of x is : " <<x <<std::endl;
cout<<"Log value of x is : "<<log(x);
return 0;
}
Output:
Value of x is : -0.5
Log value of x is : nan
In this example, value of x is -0.5. Therefore, the function log returns the Not a Number(nan).
Example 4
Let's see a simple example when the value of x is 0.
#include <iostream>
#include<math.h>
using namespace std;
int main()
{
int x= 0;
std::cout << "Value of x is : " <<x <<std::endl;
cout<<"Log value of x is : "<<log(x);
return 0;
}
Output:
clValue of x is : 0
Log value of x is : -inf
In this example, value of x is -1. Therefore, the function log returns nan(Not a Number).
Example 5
Let's see a simple example when the value of x is 0.8.
#include <iostream>
#include<math.h>
using namespace std;
int main()
{
float x=0.8;
std::cout << "Value of x is : " <<x <<std::endl;
cout<<"Log value of x is : "<<log(x);
return 0;
}
Output:
Value of x is : 0.8
Log value of x is : -0.223144
In this example, value of x is 0.8. Therefore, the function log returns the negative value i.e -0.22