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# Power Pivot Principles: The A to Z of DAX Functions – ACOT

6 July 2021

In our long-established Power Pivot Principles articles, we are starting a new series on the A to Z of Data Analysis eXpression (DAX) functions. This week it’s ACOT without a baby…

The ACOT function

This function returns the principal value of the arccotangent (inverse cotangent) of a number (which is not the same as the reciprocal of the cotangent). This needs some explanation. Consider a right-angled triangle:

Using the age-old mathematics mnemonic SOHCAHTOA, we get:

• sin x = opposite / longest side (hypotenuse) = O/H
• cos x = adjacent / hypotenuse = A/H
• tan x = opposite / adjacent = O/A
• cotan x = 1 / tan x = adjacent / opposite = A/O
• arccotan y = cotan-1 y is the angle whose cotangent is y.

This may be charted as follows:

The syntax is very simple:

=ACOT(number)

There is only one argument:

• number: the cotangent of the angle you want.