@vv How can I get rid of this problem?

@Carl Love thank you very much

Norm2 := proc (u) local x, y; z, (int(u(x, y, z)^2, [x = -Pi .. Pi, y = -Pi .. Pi, z = -Pi .. Pi]))^(1/2) end proc;
proc(u)  ...  end;
a1 := simplify(Norm2(u1)/Norm2(u0));
Error, (in simplify/recurse) ambiguous multiple assignment

why this error? 

@vv Thank you very much 

@vv thank you, but why?

a := -0.39323780;
u1 := proc (x, y) options operator, arrow; 1-exp(a*x)*cos(2*Pi*y) end proc;

u2 := proc (x, y) options operator, arrow; a*exp(a*x)*cos(2*Pi*y) end proc;

Norm2 := proc (u) options operator, arrow; (int(u^2, -.5 .. 1.5, -.5 .. 1.5))^(1/2) end proc;

simplify(Norm2(u2)/Norm2(u1));

.4266633682*sqrt(int(u2^2, [-.5 .. 1.5, -.5 .. 1.5]))
                                                      

@Mariusz Iwaniuk thank you very much

@acer thank you very much 

@Rouben Rostamian  I am saving as EPS, but it does not appear from the graphic only Axes

@Rouben Rostamian  I need transfer this figure
 

Download surf_proj_contours_M1802.mwsurf_proj_contours_M1802.mw

@Rouben Rostamian  if figure is three dimension?

@acer Thank you very much,

I used maple 18 , when i used this code ,the project of contourplot is invisible in the figure,why?

 Thank you very much, 
 

Download surf_proj_contours1.mw

 thank you very much, can i save this results as file data?

@acer u2(x,y),u1(x,y),v1(x,y) and v2(x,y) are known functions and large size , w1(x,y) =diff(v1(x,y),x)-diff(u1(x,y),y) and w2(x,y) =diff(v2(x,y),x)-diff(u2(x,y),y) , i need calcute sum(abs(w2(x,y)-w1(x,y))) for x=0..10,y=0..10, What is the correct formula that can be used?