source: downloads/boost_1_34_1/libs/math/doc/math-background.qbk @ 30

[def __form1 [^\]-1;1\[]]
[def __form2 [^\[0;+'''∞'''\[]]
[def __form3 [^\[+1;+'''∞'''\[]]
[def __form4 [^\]-'''∞''';0\]]]
[def __form5 [^x '''≥''' 0]]


[section Background Information and White Papers]

[section The Inverse Hyperbolic Functions]

The exponential funtion is defined, for all object for which this makes sense, 
as the power series 
[$../../libs/math/special_functions/graphics/special_functions_blurb1.jpeg], 
with ['[^n! = 1x2x3x4x5...xn]] (and ['[^0! = 1]] by definition) being the factorial of ['[^n]]. 
In particular, the exponential function is well defined for real numbers, 
complex number, quaternions, octonions, and matrices of complex numbers, 
among others.

[: ['[*Graph of exp on R]] ]

[: [$../../libs/math/special_functions/graphics/exp_on_R.png] ]

[: ['[*Real and Imaginary parts of exp on C]]]
[: [$../../libs/math/special_functions/graphics/Im_exp_on_C.png]]

The hyperbolic functions are defined as power series which 
can be computed (for reals, complex, quaternions and octonions) as:

Hyperbolic cosine: [$../../libs/math/special_functions/graphics/special_functions_blurb5.jpeg]

Hyperbolic sine: [$../../libs/math/special_functions/graphics/special_functions_blurb6.jpeg]

Hyperbolic tangent: [$../../libs/math/special_functions/graphics/special_functions_blurb7.jpeg]

[: ['[*Trigonometric functions on R (cos: purple; sin: red; tan: blue)]]]
[: [$../../libs/math/special_functions/graphics/trigonometric.png]]

[: ['[*Hyperbolic functions on r (cosh: purple; sinh: red; tanh: blue)]]]
[: [$../../libs/math/special_functions/graphics/hyperbolic.png]]

The hyperbolic sine is one to one on the set of real numbers, 
with range the full set of reals, while the hyperbolic tangent is 
also one to one on the set of real numbers but with range __form1, and 
therefore both have inverses. The hyperbolic cosine is one to one from __form2 
onto __form3 (and from __form4 onto __form3); the inverse function we use 
here is defined on __form3 with range __form2.

The inverse of the hyperbolic tangent is called the Argument hyperbolic tangent, 
and can be computed as [$../../libs/math/special_functions/graphics/special_functions_blurb15.jpeg].

The inverse of the hyperbolic sine is called the Argument hyperbolic sine, 
and can be computed (for __form5) as [$../../libs/math/special_functions/graphics/special_functions_blurb17.jpeg].

The inverse of the hyperbolic cosine is called the Argument hyperbolic cosine, 
and can be computed as [$../../libs/math/special_functions/graphics/special_functions_blurb18.jpeg].

[endsect]

[section Sinus Cardinal and Hyperbolic Sinus Cardinal Functions]

The Sinus Cardinal family of functions (indexed by the family of indices [^a > 0]) 
is defined by 
[$../../libs/math/special_functions/graphics/special_functions_blurb20.jpeg]; 
it sees heavy use in signal processing tasks.

By analogy, the Hyperbolic Sinus Cardinal family of functions 
(also indexed by the family of indices [^a > 0]) is defined by 
[$../../libs/math/special_functions/graphics/special_functions_blurb22.jpeg].

These two families of functions are composed of entire functions.

[: ['[*Sinus Cardinal of index pi (purple) and Hyperbolic Sinus Cardinal of index pi (red) on R]]]
[: [$../../libs/math/special_functions/graphics/sinc_pi_and_sinhc_pi_on_R.png]]

[endsect]

[section The Quaternionic Exponential]

Please refer to the following PDF's:

*[@../../libs/math/quaternion/TQE.pdf The Quaternionic Exponential (and beyond)]
*[@../../libs/math/quaternion/TQE_EA.pdf The Quaternionic Exponential (and beyond) ERRATA & ADDENDA]

[endsect]

[endsect]