How to calculate this values manually.

a=7;b=cos(a),b=cosh(a)

b =

0.7539

b =

548.3170

[Ion Stefanache]

maybe can use one approximation arraund x0=a=7 using Taylor series:

https://en.wikipedia.org/wiki/Taylor_series

Answer 1

[Akihumi]

Why not just refer to the documentations of the functions at:

https://www.mathworks.com/help/matlab/ref/double.cos.html

https://www.mathworks.com/help/matlab/ref/cosh.html

You can see the formula in More About section.