[oi)=sqa] means [the same as] oi)=das. It is also pronounced without the sigma, but with the sigma (oi)=sqas) sometimes either for the sake of meter or in order to keep a consonant from clashing.[1]
Sophocles [writes]: "you know [that you are] about to do what." Instead of poih/seis, "you will do," in Attic.[2]
And elsewhere: "you know that some who have stripped themselves in the tax offices or been altogether persuaded in the noontime of their lives by some single misfortune are accustomed to philosophize merely by making an oath or vow to God in the Platonic manner; a shadow would outstrip such men in speaking what is right."[3]
They also say e)/coisqa "you know well". Sophocles [writes]: "you also know from being present, with no one of his friends as guide, but himself leading all of us ..."[4]