How do you express symbollically that an equation doesn't have solution over the reals?

Question

This is a really quick doubt, i'm just curious about how it will be. Imagine an equation like $\cos(x)=\sqrt{-1}$, it obviously doesn't have solutions over the reals, how do I express it symbollically? (e.g using mathematical language, as $\exists$ or $\not\exists$, etc.) I've thought of something like $\not\exists x\in\mathbb{R}:\cos(x)=\sqrt{-1}$?