[size=100]At a main ceremonial gate, [b]La Puerta del Perdón[/b], of the Catedral of Granada, over a narrow street on the city, we may ask:[br][/size][br][b]Which is the correct distance to observe, at a glance (without scroll) that gate?[br][/b][br]The set of points from we can see the gate with a complete visual human angle (aprox 30 º) form a geometrical locus that is know as [b]Isoptic Curve of a segment[/b] (Arco Capaz on Spanish). This is historically associated to Pothenot Problem, and can be constructed with GeoGebra, taking in count both sides

But, instead of taking the normal geometrical locus in GeoGebra for that problem, we can generalize this by asking[br][br][b]Which is the analogous geometrical locus if we count with an human vision angle ranging from 30º to 35º [/b](as occurs in fact)[b]?[/b][br][br]The result is a locus not described at the moment (as far as we know), that we called [b]Lunula Capaz[/b] (on spanish). And we can visualize it on GeoGebra activating the trace for the following construction.