AA -»-BB + CC

Formula; modo inventœ jam aliam supcrstruemus , quœ iiiter fertilissima thcoremata in doctrina de supcrficiebus curvis referenda est. Introducamus sequentes notationes

aa -h 6i 4- ce = E ,

aa' 4- hV -+- ce' = F,

a'a' -^- Vh'^c'c'= G,

(4) rt« 4- AjS -I- cy = m,

(5) aa'-f- i/5'4-c7'= m',

(6) aa"4-A^"4-cy"= m'',

(7) a'a-h 6'jS-4-c'7= n^

(8) a'a'4-y/S'-hcy= w',