Why does proposition 1 in Euclid's Elements not end with "QEF"?

Question

I am reading from Heath's translation of Euclid's Elements. Most propositions either end with "QED" or with "QEF", when the first one is used for proving propositions that are not constructions and the second one is for constructions. However, in Heath's translation, the first three propositions (in book one) don't end with "QED" or "QEF", but with "Being what it was required to do". Why do the first three propositions end differently that all the others? Note that in other translations they don't have this issue.

Answer 1

Into Heath's edition of Elements, the first four Propositions of Bk.I end with "(Being) what it was required to do."

The original Greek formula is: ὅπερ ἔδει ποιῆσαι that reads more or less "what has to be done".

From Prop.5, see Heath's note to line 48 (page 252):

As "(Being) what it was required to prove" (or "do") is somewhat long, I shall henceforth write the time-honoured "Q. E. D." and "Q. E. F." for ὅπερ ἔδει δεῖξαι. and ὅπερ ἔδει ποιῆσαι.