If sin(x) = 1/3 and sec(y) = 29/21, where x and y lie between 0 and pi/2, what is cos(x − y)?

A3-dimensional figure has a square base and 4 lateral faces that meet at a point. explain the difference between the cross sections when a slice is made perpendicular to the base through the vertex, and when a slice is made perpendicular to the base and not through the vertex