coordinate referemce

Hi I'm doing my first macro and trying to place a coordinate reference on a layout, I want to get a cross in the center of a tank and the xy coordinates but I dont get the lines to work, any one who could help me. This is a part of the code I believe should draw my centerlines. but I get a error: bad function: when i test it.

It's my first attempt on lisp I'm not sure it's correct.

(defun c:cross ( / xyz xyz3 ptx pty ptz size x1 y1 ylin xlin uprec)

; Ask user for the number of decimal places: 

(setq uprec (getint "Label precision: ")) 


(setq xyz (getpoint "pick point: " ))
     (setq ptx (car xyz)
    pty (cadr xyz)
    pzz (caddr yxz)
    )
     (setq size (getint "Tank diameter:" ))
     
     
; Truncate values: 

(setq ptx ( ptx 2 uprec) )

(pty ( pty 2 uprec))
(ptz ( ptz 2 uprec)) 
(setq x1 (ptx - size)
    y1 ( pty - size)
    )
 (setq ylin (strcat ptx y1 pz)
xlin (strcat x1 pty ptz)
)
 (command "line" ylin )
 (command "polar" size 90 "" )
 (command "line" "polar" size 0 "")
     )


     
     

You can use the command "dimcenter" to make a cross in a circle.

Regards.

lisp tries to evaluate the first 'argument' after a ( as a function. ptx, pty, ptz are not a functions- hence the bad function

also check your variables for typos

there is no command 'Polar' in autocad

you're trying to supply a string to the line command

just a start