I could not find a simple espression that would yield the vertical dots. I did find some additional information outside of Mathematica. The three vertical dots is called a vertical ellipsis, and like the ordinary ellipsis (...) it indicates that something has been omitted. If this is the meaning in Mathematica, I must find out how retrieve the factors that were omitted. The vertical ellipsis first appeared in a very long trigonometric expression that involved orthogonal transformations between three coordinate systems, where the transformations are expressed in terms of three sets of Euler angles. Expand [ ] or TrigExpand[ ] do not eliminate the vertical ellipses and seems to introduce additional ones.
If my interpretation of the vertical ellipsis is correct, how do I find what the factors are that have been omitted? I found nothing in the online Mathematica manual.