Mathematics is full of precise and illuminating solutions to previously-confusing philosophical problems; so much so that you might call mathematics itself "precise philosophy". For example:
In general, whenever you see a "cryptic" definition of a concept in mathematics that generalizes but doesn't superficially resemble some previous concept, you're dealing with the answer to a question of the form "what is the 'philosophical essence' of concept X?"
Mathematicians have thus achieved the ultimate philosopher's dream: answers of the form "the meaning of life is 42" which are true and meaningful!
Zeno's paradoxes have been mentioned in another comment. For "theological" questions, see here.
Do you know if Plato was claiming Euclidean geometry was physically true in that sense? Doesn't sound like something he would say.
Philosophy is notorious for not answering the questions it tackles. Plato posed most of the central questions more than two millennia ago, and philosophers still haven't come to much consensus about them. Or at least, whenever philosophical questions begin to admit of answers, we start calling them scientific questions. (Astronomy, physics, chemistry, biology, and psychology all began as branches of philosophy.)
A common attitude on Less Wrong is "Too slow! Solve the problem and move on." The free will sequence argues that the free will problem has been solved.
I, for one, am bold enough to claim that some philosophical problems have been solved. Here they are: