IMARGUMENT function
Returns the argument (theta), an angle expressed in radians, such that:
Syntax
IMARGUMENT(inumber)
Inumber is a complex number for which you want the argument .
Remarks

Use COMPLEX to convert real and imaginary coefficients into a complex number.

IMARGUMENT is calculated as follows:
where:
and
z = x + yi
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example

Create a blank workbook or worksheet.

Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In the worksheet, select cell A1, and press CTRL+V.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

