# Division issue on plot due to mesh?

**URL:** <https://community.freefem.org/t/division-issue-on-plot-due-to-mesh/3045>\
**Category:** General Discussion\
**Created:** [March 16, 2024, 5:23pm UTC](https://community.freefem.org/t/division-issue-on-plot-due-to-mesh/3045 "2024-03-16T17:23:30Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Wilkinsonad01](https://avatars.discourse-cdn.com/v4/letter/w/f14d63/32.png) [@Wilkinsonad01](https://community.freefem.org/u/Wilkinsonad01)\
**Post date:** [March 16, 2024, 5:23pm UTC](https://community.freefem.org/t/division-issue-on-plot-due-to-mesh/3045/1 "2024-03-16T17:23:30Z")

</div>

Hi,  
I came a cross an issue plotting the f(x,y) = (x^2+y^2)/N  
where N is a real number

when using the code below the plots looked correct:

mesh Th = square(10,10);  
plot(Th, wait = true);

fespace U(Th, P1);  
U u;

u = (x^2 + y^2);  
plot(u, wait = true, fill = true, value = true);

u = (x^2 + y^2)/10.0;  
plot(u, wait = true, fill = true, value = true);

However when using a different mesh set up, I the two plots looked identical. For some reason the division by 10.0 did not occur:

real L = 1.0;  
int meshSize = 20;

mesh Mesh2;  
border b1(t =-1.,1.){x=L_t; y = -L;};  
border b2(t=-1.,1.){x=L; y=L_t; };  
border b3(t=0.,2.){x=L-L_t; y=L; };  
border b4(t=0.,2.){x=-L;y=L-L_t;};

Mesh2 = buildmesh(b1(meshSize) + b2(meshSize) + b3(meshSize) + b4(meshSize));  
plot(Mesh2, wait =1);

fespace U(Mesh2, P1);  
U u;

u = (x^2 + y^2);  
plot(u, wait = true, fill = true, value = true);

u = (x^2 + y^2)/10.0;  
plot(u, wait = true, fill = true, value = true);

If anyone knows why this is happening and how to fix it, please let me know.

thanks!