anchor.diff:  $$$
   x \mapsto e^x\mathrm{K}_1(x)
   
  +#### Struve functions
  +
  +Struve functions are solutions $y(x)$ of the non-homogeneous Bessel's differential equation
  +
  +$$$
  +x^2\frac{\mathrm{d}^2y}{\mathrm{d}x^2}+x\frac{\mathrm{d}y}{\mathrm{d}x}+(x^2-\alpha^2)y = \frac{4(\frac{x}{2})^{\alpha+1}}{\sqrt{\pi}\Gamma(\alpha+\frac{1}{2})}
  +
   
   #### Modified Struve functions
   
  -Struve functions are solutions $y(x)$ of the non-homogeneous Bessel's differential equation
  -
  -$$$
  -x^2\frac{\mathrm{d}^2y}{\mathrm{d}x^2}+x\frac{\mathrm{d}y}{\mathrm{d}x}+(x^2-\alpha^2)y = \frac{4(\frac{x}{2})^{\alpha+1}}{\sqrt{\pi}\Gamma(\alpha+\frac{1}{2})}
  +Modified equation:
  +
  +$$$
  +x^2\frac{\mathrm{d}^2y}{\mathrm{d}x^2}+x\frac{\mathrm{d}y}{\mathrm{d}x}-(x^2+\alpha^2)y = \frac{4(\frac{x}{2})^{\alpha+1}}{\sqrt{\pi}\Gamma(\alpha+\frac{1}{2})}
   
   Modified Struve functions:
   
  
positive.code: Bessel and Struve Functions
  ---------------------------
  
  #### Modified Bessel functions
  
  Bessel functions are canonical solutions $y(x)$ of Bessel's differential equation
  
  $$$
  x^2\frac{\mathrm{d}^2y}{\mathrm{d}x^2}+x\frac{\mathrm{d}y}{\mathrm{d}x}+(x^2-\alpha^2)y = 0
  
  Modified Bessel functions:
  
  
negative.code: $$$
  (a,b) \mapsto \sqrt{a^2 + b^2}
  
  
  Trigonometry
  ------------
  
  The `Trig` class provides the complete set of fundamental trigonometric functions
  for both real and complex arguments.
  
  * **Trigonometric**: Sin, Cos, Tan, Cot, Sec, Csc
  * **Trigonometric Inverse**: Asin, Acos, Atan, Acot, Asec, Acsc
  * **Hyperbolic**: Sinh, Cosh, Tanh, Coth, Sech, Csch
  * **Hyperbolic Area**: Asinh, Acosh, Atanh, Acoth, Asech, Acsch
  * **Sinc**: Normalized sinc function $x \mapsto \frac{\sin\pi x}{\pi x}$
  * Conversion routines between radian, degree and grad.
  
  *)
  