C++ Math log() Function

C++ Math log() Function with tutorial for beginners and professionals with examples on isgreaterequal(), less(), islessequal(), islessgreater(), isunordered(), exp(), frexp(), ldexp(), log(), log10(), modf(), exp2(), expm1(), log1p(), log2(), logb(), scalbn(), scalbln() etc.

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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

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C++ Math log() Function

C++ Math log()

Mathematically:

Syntax

Parameter

Return value

Example 1

Example 2

Example 3

Example 4

Example 5

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.Net

Java

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