Hyperbolic Functions

Definitions

The hyperbolic functions are defined as:

The graphs of hyperbolic functions are below:

y=sinhxxyy=coshxxy1y=tanhxxy1-1

From these graphs, the domain and range of the hyperbolic functions can be found:

  • has a domain of , range of .
  • has a domain of , range of .
  • has a domain of , range of .

Inverse hyperbolic functions

The inverse hyperbolic functions are , , and , also denoted and respectively.

y=arsinhxxyy=arcoshxxy1y=artanhxxy-11

The domains and ranges can be found:

  • has a domain of , range of .
  • has a domain of , range of .
  • has a domain of , range of .

The inverse hyperbolic functions have logarithmic forms that can be proved by using the exponential definition of the hyperbolic functions and solving the hidden quadratic. These are:


  • These are given in the formula book. Proofs are given below.

Hyperbolic identities

The most important hyperbolic identity is:

When proving identities, it is often useful to return to the exponential definitions of , , and . Outside of the syllabus, there is Osborn's Rule for converting normal trigonometric identities into hyperbolic identities.

Calculus of hyperbolic functions

The derivatives of hyperbolic functions are:


  • Only the last one is given. These can be found by returning to the exponential definitions.

The integrals of hyperbolic functions are:

Derivation of logarithm definitions of inverse hyperbolic functions

The following proofs are given to derive the logarithm definitions of inverse hyperbolic functions. Broadly, all follow a similar idea of completing the square on (this can even be used to find logarithmic definitions of inverse trigonometric functions, which has come up before on past papers).

Proof for
Proof for