Within the world of complex numbers, the 'imaginary' value, i is used to represent the square root of 1.
A Complex Number is composed of a real number combined with an imaginary number.
E.g. The complex number, z, is written as
The Excel IMREAL function returns the real coefficient of a supplied complex number.
I.e. the function returns the value a, for the complex number a + bi.
The syntax of the Imreal function is:
where the inumber argument is a Complex Number.
Note that complex numbers are simply stored as text in Excel. When a text string in the format "a+bi" or "a+bj" is supplied to one of Excel's builtin complex number functions, this is interpreted as a complex number.
Also the complex number functions can accept a simple numeric value, as this is equivalent to a complex number whose imaginary coefficient is equal to 0.
Therefore, the inumber argument can be supplied to the Excel Imreal function as either:
In the example spreadsheets below, the Excel Imreal function is used return the real coefficient of five different complex numbers.
Formulas:

Results:

Note that, in the above example spreadsheet:
Further details of the Excel Imreal function are provided on the Microsoft Office website.
If you get an error from the Imreal function, this is likely to be one of the following:
#NUM!    Occurs if the supplied inumber argument is not recognised as a complex number. 
#VALUE!    Occurs if the supplied inumber argument is a logical value. 