code: def getArc(prom, sig, mc, pos, zerolat):
      
      pRA, pDecl = prom.eqCoords(zerolat)
      sRa, sDecl = sig.eqCoords(zerolat)
      mcRa, mcDecl = mc.eqCoords()
      return arc(pRA, pDecl, sRa, sDecl, mcRa, pos.lat)
docs: Returns the arc of direction between a promissor
      and a significator. Arguments are also the MC, the
      geoposition and zerolat to assume zero ecliptical 
      latitudes.
      
      ZeroLat true => inZodiaco, false => inMundo