Let the height of the prism be H, V=48 and the bottom area be 8, then h = 6...(4 points).

As shown in the figure, if connecting B 1A, ∠DB 1A is the required angle, …(6 points)

∴ Tan α = Adab 1 = 3 10, ... (10)

So α = arctan310 ... (12 points)