expm1
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header  
<math.h>
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|   float       expm1f( float arg ); 
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(since C99) | |
|   double      expm1( double arg ); 
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(since C99) | |
|   long double expm1l( long double arg ); 
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(since C99) | |
Computes the e (Euler's number, 2.7182818) raised to the given power arg, minus 1. This function is more accurate than the expression exp(arg)-1 if arg is close to zero.
[edit] Parameters
| arg | - | floating point value | 
[edit] Return value
earg
-1
If the result is too large for the underlying type, range error occurs and HUGE_VAL is returned.
[edit] See also
|    returns e raised to the given power (ex)   (function)  | 
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|    (C99) 
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   returns 2 raised to the given power (2x)   (function)  | 
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C++ documentation for expm1
 
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