I am reading a book on total synthesis. I do not know what a type of notation used for unsaturated bonds means. The notation is :delta:(triangle)1,2. I picked 1,2 arbitrarily. Here is an example from the book:
"Saturation of the electron-deficient :delta:14,15 double bond in 30 with hydrogen in the presence of palladium on charcoal provides, as the major product, cis ester 31 and a small amount of the isomeric trans ester."