Ottofire, the translation given by the NAS here is not good. (Usually the NAS is much better than the KJV or NIV, but not in this case.) The direct object of the clause in verse 4 is the Greek word "asphaleian", which is used three times in the NT. It means "assurance", "certainty", "firmness", or "security". It does not mean "exact truth". A better translation of verse 4 is: "so that you come to know the certainty concerning the words which you were taught [orally]." There is no Greek word there that should be translated "exact truth".
-A8
--Ottofire, the translation given by the NAS here is not good. (Usually the NAS is much better than the KJV or NIV, but not in this case.) The direct object of the clause in verse 4 is the Greek word "asphaleian", which is used three times in the NT. It means "assurance", "certainty", "firmness", or "security". It does not mean "exact truth". A better translation of verse 4 is: "so that you come to know the certainty concerning the words which you were taught [orally]." There is no Greek word there that should be translated "exact truth".
So I should state: Luke is writing to Theophilus to give him the assured, certain, firm and/or secure truth.
I am not a Greek scholar in the least, and I will accept your findings unless someone else IS a Greek scholar and says otherwise. Exact does seem like a more modern term, much like the word Magnify, can add connotations that might not be there... :o)