It seems pretty obvious though for anyone contemplating the problem however briefly that "c" can be as large as one wishes, but it cannot be smaller than the minimum needed to connect the inner and outer squares (for the case they're in the same plane / height is zero). Not being able to handle the negative root is understandable but one would have expected Heron to realize there are "off limits" cases for his formula...
It seems pretty obvious though for anyone contemplating the problem however briefly that "c" can be as large as one wishes, but it cannot be smaller than the minimum needed to connect the inner and outer squares (for the case they're in the same plane / height is zero). Not being able to handle the negative root is understandable but one would have expected Heron to realize there are "off limits" cases for his formula...