Implied question: It says in Megilah (27b) that R. Freida's Talmidim asked him in what merit he lived so long, and he said "no one ever came to the Beis Midrash before me"!

Answer #1: That, and this episode (teaching the Talmidim 800 times) both caused it.

Answer #2: At that time he did not know that Hash-m told [the angels] "give to him both of these", until after he lived 400 years.

Assertion: Also if there is one protrusion (house), we view it as if there is another protrusion opposite it, and we extend the line (the extent of the city) between them. We do not extend a line on a diagonal from the protrusion to the other end of the city.

Source: If it is wide on one side, we view it as if it is even, and if it is circular, we view it as if it is square.

Support: Now, we ask properly. For one protrusion [we extend that entire side]. All the more so we do so for two! (Without Tosfos' Chidush, this would not be a question, for we would add more due to the second protrusion.)