This information is part of the Modelica Standard Library maintained by the Modelica Association.
This function returns the area hyperbolic cosine of its input argument u. The valid range of u is
+1 ≤ u < +∞
If the function is called with u < 1, an error occurs. The function cosh(u) has two inverse functions (the curve looks similar to a sqrt(..) function). acosh(..) returns the inverse that is positive. At u=1, the derivative dy/du is infinite. Therefore, this function should not be used in a model, if u can become close to 1: