====== Some important series of functions ======
On this page we are going to post some series of functions, which are used in mathematics at undergraduate level.

  * $\sinh x =  x +  \frac{x^3}{3!} + \frac{x^5}{5!} + \frac{x^7}{7!} +... \qquad -\infty <x< \infty$
  * $\cosh x =  1 + \frac{x^2}{2!} + \frac{x^4}{4!} + \frac{x^6}{6!} +... \qquad -\infty <x< \infty$
  * $\tanh x =  x -  \frac{x^3}{3} + 2\frac{x^5}{15} - 17\frac{x^7}{315} +... \qquad \left |x\right |< \frac{\pi}{2}$
  * $\coth x =  \frac{1}{x} + \frac{x}{3} - \frac{x^3}{45} +... \qquad   0 <x< \pi$
  * $\mathrm{sech} x = 1-\frac{x^2}{2}+\frac{5x^4}{24}-\frac{61x^6}{720} +... \qquad \left |x\right |<\frac{\pi}{2}$
  * $\mathrm{csch} x = \frac{1}{x}-\frac{x}{6}+\frac{7x^3}{360} -... \qquad 0<\left |x\right |<\pi$
  * $\sinh^{-1} x = \pm{ln\left |2x\right |+\frac{1}{2.2x^2}-\frac{1.3}{2.4.4x^4} +...}$ + if $x\geq 1$,                                                           - if $x\leq 1$
  * $\cosh^{-1 }x = \pm{ln(2x)-(\frac{1}{2.2x^2}+\frac{1.3}{2.4.4x^4} +. . .}$
  * $\tanh^{-1} x = x+\frac{x^3}{3}+\frac{x^5}{5}+\frac{x^7}{7} +. . . \qquad \left |x\right |<1$
  * $\coth^{-1} x =  \frac{1}{x}+\frac{1}{3x^3}+\frac{1}{5x^5}+\frac{1}{7x^7} +... \qquad \left |x\right |>1$