IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html
At:
exteq sum family singleton vs intseg1 1. a :
2. a' :
3. a'-a = 1
4. B : {a..a'}Type
(i:{a..a'}B(i)) =ext ({a:}B(a))
By:
Analyze THEN Analyze
THEN
New:[i | b] Analyze-1 THEN Analyze
THEN
Try BackThru: Thm*a,a':. a'-a = 1 ({a..a'} =ext {a:})