tanh (<valarray>)

Article
07/11/2012

Operates on the elements of an input valarray, returning a valarray whose elements are equal to the hyperbolic tangent of the elements of the input valarray.

template<class Type> 
   valarray<Type> tanh( 
      const valarray<Type>& _Left 
   );

Parameters

_Left
The input valarray whose elements are to be operated on by the member function.

Return Value

A valarray whose elements are equal to the hyperbolic cosine of the elements of the input valarray.

Remarks

Identities defining the hyperbolic tangent in terms of the exponential function:

tanh ( z ) = sinh ( z ) / cosh ( z ) = ( exp ( z ) – exp ( -z ) ) / ( exp ( z ) + exp ( -z ) )

Example

// valarray_tanh.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>
#include <iomanip>

int main( )
{
   using namespace std;
   double pi = 3.14159265359;
   int i;

   valarray<double> va1 ( 9 );
   for ( i = 0 ; i < 9 ; i++ ) 
      va1 [ i ] =  pi * ( 0.25 * i - 1 );
   valarray<double> va2 ( 9 );

   cout << "The initial valarray is:\n";
   for ( i = 0 ; i < 9 ; i++ )
      cout << setw( 10 ) << va1 [ i ]
      << "   radians, which is     "
                    << setw( 5 ) << ( 180/pi ) * va1 [ i ]
                    << "  degrees" << endl;
   cout << endl;

   va2 = tanh ( va1 );
   cout << "The hyperbolic tangent of the initial valarray is:\n";
   for ( i = 0 ; i < 9 ; i++ )
     cout << va2 [ i ] << endl;
}

The initial valarray is:
  -3.14159   radians, which is      -180  degrees
  -2.35619   radians, which is      -135  degrees
   -1.5708   radians, which is       -90  degrees
 -0.785398   radians, which is       -45  degrees
         0   radians, which is         0  degrees
  0.785398   radians, which is        45  degrees
    1.5708   radians, which is        90  degrees
   2.35619   radians, which is       135  degrees
   3.14159   radians, which is       180  degrees

The hyperbolic tangent of the initial valarray is:
-0.996272
-0.982193
-0.917152
-0.655794
0
0.655794
0.917152
0.982193
0.996272

Requirements

Header: <valarray>

Namespace: std

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