Cyr., 3., 3., 39

Specific Text Questions Cyropaedia
1

ὑμεῖς γὰρ καὶ πλησιάζετε αὐτοῖς ἕκαστος τῷ ἑαυτοῦ μέρει
Is this D of space or instrumental?

2

αυτοῖς just the regular dative with πλησιάζειν.
τῷ ἑαυτοῦ μέρει instrumental.