# ggT: Calculates the greatest common divisor of two natural numbers... In cycloids: cycloids

## Description

The function ggT calculates the greatest common divisor of two natural numbers. In this package it is called by the function `kgV` which calculates the least common multiple of two natural numbers. The latter is needed by the function `zykloid` and by the function `npeaks` which calculates the number of peaks (or loops) a cycloid has. As the greatest common divisor might be useful for other purposes, the function ggT is accessible to external use in this package.

## Usage

 `1` ```ggT(a, b) ```

## Arguments

 `a` A natural number (integer value > 0) `b` A natural number (integer value > 0)

## Value

A natural number if a and b are natural numbers. In any other case, the function returns NA.

Peter Biber

## References

Bronstein IN, Semendjaev KA, Musiol G, Muehlig H (2001): Taschenbuch der Mathematik, 5th Edition, Verlag Harri Deutsch, 1186 p. (p. 333)

http://en.wikipedia.org/wiki/Euclidean_algorithm

`kgV`, `npeaks`
 ```1 2 3 4 5 6 7 8``` ```ggT(18, 6) # 6 ggT(38, 105) # 1 ggT(36, 9) # 9 ggT(12, 9) # 3 ggT(9, 12) # 3 ggT(-5, 12) # NA - only integer numbers > 0 allowed ggT(3, 0) # NA - only integer numbers > 0 allowed ggT(3.2, 12) # NA - only integer numbers > 0 allowed ```