How do I take the inverse cosh of a number?

Question

I am solving an electromagnetics equation for Chebysheve transformers. My equation I need to solve is:
sec(theta)m = cosh [1/3 cos h ^-1 (1.73 E -01)]
I am not familiar with the sinh, cosh, tanh, etc functions and am unsure how to evaluate the right side of the equation on my scientific calculator. What is the cosh function, and how would I evaluate it on my scientific calculator (TI-83)?
Thank you.

Answer 1

cosh x= 1/2(e ^x+e^-x) so cosh x is aways>=1 and is an even function
and its inverse cosh^-1 (x) =ln[x+-sqrt(x^2-1)]
Look for hyperbolic functions on your calculator and the 2nd function key
supposing that you have cosh^-1(1.73) = +-1.1448

Answer 2

Inverse Cosh