ACOSH

The Excel ACOSH function returns the inverse hyperbolic cosine of a number. Given the input 2.0, the function returns the value 1.316957897. Given the x-component of a point that lies on the right branch of the unit hyperbola given by the equation x² - y² = 1, the ACOSH function returns the hyperbolic angle formed by the point. In other words, the ACOSH function returns twice the area of the sector formed between the origin, the x-axis, and the point on the hyperbola. Images courtesy of wumbo.net.