The Excel ACOT Function

Related Function:
COT Function
Arccotangent

The Arccotangent is the inverse of the cotangent.

Therefore, for the simple right-angled triangle below, the arccotangent of the adjacent side, a, divided by the opposite side, o, is equal to the angle θ.

Right-Angled Triangle

I.e. for the triangle above,

Arccotangent Equation
The Inverse trig. functions are discussed further on the Wikipedia Inverse Trigonometric Functions Page

Basic Description

The Excel Acot function calculates the arccotangent (i.e. the inverse cotangent) of a given number, and returns an angle, in radians, between 0 and π.

Note: the Acot function was only introduced in Excel 2013 and so is not available in earlier versions of Excel.

The syntax of the function is:

ACOT( number )

Where the number argument is the value that you want to calculate the arccotangent of.

Converting from Radians to Degrees

If you want the angle returned by the Acot function to be expressed in degrees, you can convert it, using the Excel Degrees function:

=DEGREES( radians )
An example of this is given below.

Excel Acot Function Examples

The following spreadsheet shows the Excel Acot Function, used to calculate the arccotangent of four different values:

 Formulas:
 A
1=ACOT( 1 )
2=ACOT( -2 )
3=ACOT( 0 )
4=DEGREES( ACOT( 0 ) )
 Results:
 AB
10.785398163- Result is π/4 radians
22.677945045 
31.570796327- Result is π/2 radians
490- Result is 90 degrees

Note that, in cell A4 of the above spreadsheet, the Excel Degrees function is used to convert the Acot function result from radians into degrees.


For further details and examples of the Excel Acot function, see the Microsoft Office website.


Acot Function Error

If you get an error from the Excel Acot function, this is likely to be the #VALUE! error:

Common Error
#VALUE!-Occurs if the supplied number argument is non-numeric.