A function is known to fit closely to the approximate function

It is fitted to the three points (z = 0, f = 1), (z = 0.5, f = 1.128) and (z = 1.3, f = 1.971). Show that the parameters satisfy

Find a, b and c and hence the approximating function (use of MATLAB is recommended). Check the value f(1) = 1.543. (Note that the values were chosen from tables of cosh z.) The method described here is a simple example of a powerful approximation method.