Why is there no case agreement between "magni" and "poetae"?

Question

Shouldn't "magni" be "magnae" as it is modifying "poetae"?

Fīliae vestrae dē libris magnī poētae saepe cogitābant.

The quote is from Wheelock's Latin, chapter 6.

Answer 1

There is agreement, in fact! Both of these words are masculine genitive singular.

The trick is that poēta is a masculine noun, despite being in the first declension. So the genitive singular is -ae, just like puellae. But agreement depends on gender, not declension, so it takes the masculine -ī, just like puerī.