Find the Nth term of the series 2, 15, 41, 80, 132...

log2() function in C++ with Examples

Last Updated : 04 May, 2020

The function log2() of cmath header file in C++ is used to find the logarithmic value with base 2 of the passed argument.

Syntax:

log2(x)

Parameters: This function takes a value x, in the range [0, ∞] whose log value is to be found.

Return Type: It returns the logarithmic value, as double, float or long double type, based on the following conditions:

If x > 1: It returns the positive logarithmic value of x.
If x is equals to 1: It returns 0.
If 0 < x < 1: It returns the negative logarithmic value of x.
If x is equals to 0: It returns the negative infinity(-∞).
If x < 0: It returns NaN(Not a Number).

Below examples demonstrate the use of log2() method:

Example 1:

// C++ program to illustrate log2() function 
  
#include <bits/stdc++.h> 
using namespace std; 
  
// Driver Code 
int main() 
{ 
    long b = 16; 
    float c = 2.5; 
    double d = 10.35; 
    long double e = 25.5; 
  
    // Logarithmic value of long datatype 
    cout << log2(b) << "\n"; 
  
    // Logarithmic value of float datatype 
    cout << log2(c) << "\n"; 
  
    // Logarithmic value of double datatype 
    cout << log2(d) << "\n"; 
  
    // Logarithmic value of long double datatype 
    cout << log2(e) << "\n"; 
  
    return 0; 
} 

Output:

Example 2:

// C++ program to illustrate log2() function 
  
#include <bits/stdc++.h> 
using namespace std; 
  
// Driver Code 
int main() 
{ 
    // To show extreme cases 
    int a = 0; 
    int b = -16; 
  
    // Logarithmic value of 0 
    cout << log2(a) << "\n"; 
  
    // Logarithmic value of negative value 
    cout << log2(b) << "\n"; 
  
    return 0; 
} 

Output:

-inf
nan

Reference: http://www.cplusplus.com/reference/cmath/log2/

Find the Nth term of the series 2, 15, 41, 80, 132...

A

akash_garg

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