SMCADMAN'S response was sweet and to the "point". This is the same way I do it. However, before I extrude my base triangle, I place a line at the center the exact height I need it, then select a UCS with the base of that line, a corner of the triangle (x) and the upper end of the line (Y). I then do a simple angle dim and extend the number of decimals available to 8. I then use all 8 in my angle answer for the extrude command. SMCADMAN was right that the answer is very simple and straight forward. I might only add that there are more parts and shapes to be created than can be programmed into any one automated function or command. Yesterday a designer I work with was stymied because his high-end modeler wouldn't create a particular shape with a particular orientation to a particular axis reference. I showed him how I'd create the part in basic ACAD, and suggested he look for similar elements in his PRO-E modeler. He not only was able to create the part effectively in PRO-E, the novel approach offered him 2 new parametric relationships he was able to take advantage of that he wouldn't have discovered using only limited pre-programmed construction solutions. ACAD may honestly be a slower second cousin to the genuinely more powerful PRO-E (and others ...) but part modeling is more about what you can create to solve the boss's problems. Good luck and thanks for the opportunity to share...
cfee