The Gemara explains why we don’t add another bracha to Havineinu on motzei Shabbos (for havdala) since Havineinu was established specifically as a ‘seven bracha unit’ and not eight. If Havineinu assumes a new identity as a ‘seven bracha tefilla’ then why doesn’t the Gemara require a source corresponding to this number as the Gemara sought regarding the various types of shemone esrei (i.e. 18 of weekdays, 7 of Shabbos etc.)?
The Gemara says one can recite Havdalah while it is still day (Shabbos). If Havdalah is meant as a separator between Shabbos and the weekdays, how can this be done while it is still day?
The Gemara relates how the student approached Rabban Gamliel to ask regarding Tefillas Arvis, and then proceeded to ask the same question of Rabbi Yehoshua. How is one allowed to approach another Rav with the same question already responded to by a previous Rav (see Avoda Zarah 7a)?