Recently I came across a rebus that went like this: $$\sqrt{-1} \ 2^3 \ \sum \pi$$ $$ \text{ and it was delicious! }$$ Here is the answer (first try yourself):
I ate some pie and it was delicious!
A more sophisticated one can be found here https://puzzling.stackexchange.com/questions/15862/mathematical-rebus
I was wondering if there are more of these examples that require a certain level (going beyond the layman's knowledge) of education in mathematics.
The comic called Spiked Math has quite a lot of its stripes based on stuff like this (although other things than formulas certainly appear). For instance, he has made five movie math quizzes that can be easily found in the archives since they're titled "The Movie Math Quiz $n$". I can't speak for the mathematical level needed to solve them, though.