ἐμπειρέω
From LSJ
προγράψαντες οὖν τά τε θεωρήματα καὶ τὰ ἐπιτάγματα τὰ χρεῖαν ἔχοντα εἰς τὰς ἀποδείξιας αὐτῶν μετὰ ταῦτα γραψοῦμές τοι τὰ προκείμενα → having therefore written at the beginning the theorems and the postulates that are necessary for their proofs, we will then write out for you the propositions
English (LSJ)
A to be experienced in, have knowledge of, c. gen. rei, τῆς χώρας Plb.3.78.6, etc.; τῆς ὁδοῦ LXXTo.5.6.