１．Let's try to picture using Decimal BASIC

　Consider a square with sides of 1 unit length.
　Let's try to picture how the diagram of this figure is changed using complex function
　　　w=z².
　Choose
　　　OPTION ARITHMETIC COMPLEX
in the introduction of the program in Decimal BASIC in order to set to complex number mode.

　Then a complex number,
　　　z=x+iy
can be written are gotten in z=complex(x,y).
　And, by defining a function as
　　　w=z²,
a complex number after the change can be found.
Then describe the real and imaginary part,
　　　Re(w), Im(w)
After taking out the real part and the imaginary part, let's picture the figure after the change.
　Consider how the tracing of a squre figure is modified by this program.


OPTION ARITHMETIC COMPLEX               ! It sets to the complex number mode

SET WINDOW -2,2,-1,3

DRAW grid

SET LINE STYLE 1

SET LINE COLOR 1

PLOT LINES: 0,0 ; 1,0 ; 1,1 ; 0,1; 0,0  !The original diagram

SET POINT STYLE 3

Do

   MOUSE POLL x,y,left,right

   if right=1 then exit do              !It ends by the mouse right button click.

   if left=1 then

      SET POINT COLOR 1

      PLOT POINTS: x , y

      LET z=COMPLEX(x,y)                !The function for the complex number

      LET w=z^2                         !The definition with changing function

      SET POINT COLOR 4

      PLOT POINTS: Re(w),Im(w)          !The show of the point after the change

   end if

Loop

END

　Let's try to execute. Trace a square side skillfully. How is it? The changed figure appeared.

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