Lecture
This lecture focuses on the attachment of a standard cell, specifically when the space A is a sphere and the attaching space is the cone over this sphere, which is homeomorphic to a disk. The instructor explores the implications for cells of dimension greater than or equal to 3, then for 2-cells, and finally for 1-cells, using the Seifert-van Kampen theorem. Different results are observed based on the dimension of the cells. For cells of dimension 3 or higher, the fundamental group remains unchanged, as demonstrated by the triviality of the fundamental group of Sn-1. The lecture also covers the fundamental group calculation of RP3, the real projective space of dimension 3, showing that attaching a cell of dimension 3 does not alter the fundamental group.