Namely? I can only see on word in dat.(and it could be gen. too), "texnain".
Texnain is gen. or dat. of dual number.
s. d. pl.
nom. τεχνη τεχνα τεχναι
gen. τεχνης τεχναιν τεχνων
dat. τεχνηι τεχναιν τεχναις
acc. τεχνην τεχνα τεχνας
voc. τεχνη τεχνα τεχναι
In our case I think it is safe to say we're talking about the dat. case.
How do we know? By analyzing this sentence syntactically we can find the answer.
Starting from our verb, which is epaideusas (-a, -as, -e(n), -amen, -ate, -an), aorist indicative active second person, we understand the subject to be "you". Sy epaideusas = You taught.
Our object is "tous philous" which means the friends, or those who love. "Logwn" is gen. and defines "philous". Since you gave no context I can't be sure what the author is saying, but I'm thinking "logous" might refer to "rhetorics", so we'll just translate so far as "Sy epaideusas tous philous logwn" = "You taught the friends of rhetorics", or "You taught those who love rhetorics".
Now for the final key word, "texnain", it seems like its in dat. case because it defines "epaideusas" and indicates the way "you taught". It's called a "dativus instrumenti" in latin and indicates the instrument or mean of an action. So this "texnain", in our case is a dat. in dual number, that indicates how "you taught", so we should loosely translate as:
"Using 2 artifices, you educated(taught) those who love rhetorics."
Now I'm not entirely happy with this translation, and things would be much easier and convenient if instead of "texnain" we had "texna" or "texnas", but that's what the sentence you wrote is saying.