6. Cui dedisti librum quem magister dīxit mihi legendum esse?
I think mihi here is a dative of agent with the passive periphrastic, so I have "To whom did you give the book that the master said must be read by me?"
Two questions: how would you say
(a) ".... the book that the master said must be read to me"?
(b) ".... the book that the master told me must be read [generally, not just by me]"?
You've understood the sentence correctly. And I think the questions you're asking are really good ones.... The way to master a construction is to learn it in relation to other constructions; to figure out, "Why does it mean this, and not that? How would you make it mean that?"
In this case though, most of the sentences (including the one from the book) are a bit clunky and unnatural.... It is hard to imagine anyone wanting to say these things in order to actually communicate something. So we should recognize that much of the difficulty is contrived and unlikely to arise in real life. To start with, instead of, Magister dixit hunc librum mihi legendum esse
(the teacher said that this book must be read by me), a Latin speaker would probably say, Magister me hunc librum legere iussit,
or Magister praecepit ut hunc librum legerem
, using verbs of commanding or instructing. (I'm not sure which verb is most natural in describing what a teacher does.) That would eliminate the ambiguity of whether mihi
is the indirect object of a verb of saying, or the dative of agent with the passive periphrastic. (To make the examples clearer, I've made them a main clause instead of subordinate to Cui dedisti librum...?
, which adds unnecessary complication.)
So, coming finally to your two examples:
(a) If the sentence is, "To whom did you give the book that the teacher said must be read to me?" I'm not sure that you can
say this in Latin without ambiguity. If it is to be read to me by you
, you could say, Cui dedisti librum quem magister te mihi legere iussit?
(To whom did you give the book which the teacher told you to read to me?) Or, leaving the agent unspecified, you could say, Cui dedisti librum quem magister dixit mihi legi oportere?
(To whom did you give the book that the teacher said must be read to me?)
(b) This gets into your second question. You can also express obligation using oportet
with accusative and infinitive, and it's quite common to leave out the person by whom it must be done. So you could say, Cui dedisti librum quem magister dixit legi oportere?
, which means, "...the book that must be read [generally]."
One last point: although passive periphrastics are passive in Latin, often their best equivalent in English is an active sentence. So, your original sentence from the book is really best rendered as, "To whom did you give the book that the teacher said I had to read?"