There's more...

First, in order to convert these column calculations to measures, simply replace the first two lines of each formula with the following:

VAR __x = MAX('R06_Table'[x])
VAR __y = MAX('R06_Table'[y])

Second, if given polar coordinates in radians and radius, we can convert these to Cartesian coordinates using the following column formulas:

x' = 
    VAR __r = 'R06_Table'[r]
    VAR __theta = 'R06_Table'[theta]
RETURN
    ROUND( __r * COS( __theta ) , 2)

y' = 
    VAR __r = 'R06_Table'[r]
    VAR __theta = 'R06_Table'[theta]
RETURN
    ROUND( __r * SIN( __theta ) , 2)

Finally, the angular portion of polar coordinates is generally expressed in either radians or degrees. We can convert our theta column to degrees using DAX's DEGREES function, as in the following column formula:

Degrees = 
    VAR __theta = 'R06_Table'[theta]
RETURN
    DEGREES(__theta)

We can also convert degrees to radians using DAX's RADIANS function, as in the following column formula:

theta' = 
    VAR __degrees = 'R06_Table'[Degrees]
RETURN
    RADIANS( __degrees )