Top angle and Curb angle

[Alirashid]

Is the Top angle and Curb Angle same or different?

 

[JStephen]

Refer to Figure 5.24 and Table 5.20a. There they term configuration "a" as a top angle, configuration "b" as a curb angle.
Generally, I'd call any angle at or near the top of the tank a top angle, and don't use the term "curb angle".