Home » Excel-Built-In-Functions » Excel-Math-Functions » Excel-Acos-Function

Search this site: Custom Search

Arccosine The Arccosine is the inverse of the cosine. Therefore, for the simple right-angled triangle below, the arccosine of the adjacent side, a, divided by the hypotenuse, h, is equal to the angle θ. i.e. for the triangle above, The Inverse trig. functions are discussed further on the Wikipedia Inverse Trigonometric Functions Page

Basic Description

The Excel ACOS function calculates the arccosine (ie. the inverse cosine) of a given number, and returns an angle, in radians, between 0 and π.

The format of the function is :

Where the Number argument is the value, between -1 and +1, for which you want to calculate the arccosine.

Example

Column A of the spreadsheet below, shows examples of the Excel Acos Function, used to calculate the arccosine of different values. In the example in cell A4, the result is converted from radians, into degrees.

The formulas are shown in the spreadsheet on the left and the results are shown in the spreadsheet on the right.

Further information and examples of the Excel Acos function can be found on the Microsoft Office website.

Common Error

If you get the #NUM! error from your Excel Acos function this is likely to be because the supplied Number argument is not in the range -1 to +1.