@brownr it is a pain!

@Prebein Alsholm it easy in maple a simmetrical tolerance, for example 10+-1, but id i want 10+2, 10-1, how i can put it in Maple?. Thanks!

@vv  a clever method vv. I'm studying a solar PV installation with Maple. It is important to know the losses due to shadows between pv panel. It is the reason which i need to know the projectin onto a surface. I will take account both method. It you want, i will post a example or result. Thanks

@Rouben Rostamian  I am currently using a similar procedure, in the next few days I am sending it. Thank you Rouben!!!

@vv I was referring to a cube or dodecahedron or similar geometric figure represented with maple, not two horses....i need to get the shadow no a photography

@Rouben Rostamian for instance, if you want to get the "shadow" of a 2D or 3D object onto a surface with equation z=f(x,y)

@vv 

I´ll try to modify de model. Thank you very much!

Is it possible to improve this rounding error?. What do you think about this?

Example_with_ploblem_with_implicitplot_and_Lambert_W_function.mw@miguelbravo 

Problem_with_implicitplot.pdf

Problem_with_implicitplot.pdf@gkokovidis 

Thank you very much, i will try to solve it again by reorder it.

@tomleslie  Ah!, 

OK, it is a convex optimization problem

@tomleslie  how can i do if the constraint is w+x+y+z>=5?. It is different to   w+x+y+z<=5!!!!!!.         Thanks!!!!

@YasH  NLP Is Non Linear Programing