The function "arcosh," short for "inverse hyperbolic cosine," is a mathematical function that helps find the angle whose hyperbolic cosine is a given number. It is denoted as arcosh(x) and is defined for values of x greater than or equal to 1. The formula for arcosh can be expressed as arcosh(x) = ln(x + √(x² - 1)), where ln represents the natural logarithm. The hyperbolic cosine function, denoted as cosh, is similar to the regular cosine function but is based on hyperbolic geometry. The arcosh function is useful in various fields, including mathematics, physics, and engineering, particularly in problems involving hyperbolic functions and their applications.