Levenberg–Marquardt algorithm - cosinus function

Here, I post a low-level Levenberg–Marquardt algorithm for fitting the cosinus function.

The sinus and cosinus functions are very frequent in optical disciplines like interferometry and electronics. Therefore, it is necessary to know the basics principles how the non-linear least squares algorithms are working. Here, I post Levenberg–Marquardt algorithm for fitting the cosinus function. The presented algorithm fits amplitude, phase and offset of cosinus function. The algorithm itself was taken from study material of Technical University of Denmark published by K. Madsen, H.B. Nielsen, and O. Tingleff. Please see their on-line material "METHODS FOR NON-LINEAR LEAST SQUARES PROBLEMS" (web page: <http://www2.imm.dtu.dk/pubdb/edoc/imm3215.pdf>).