You're talking about a metric tensor on a pseudo-Riemannian manifold, I'm talking about a metric space. A metric in the sense of a metric space takes nonnegative real values. If you relax the condition that distinct points have nonzero distance, it's a pseudometric.
That's not relevant to what they said, which is that distances can't be imaginary. They're correct. A metric takes nonnegative real values by definition
CSS is still used. Modern web toolkits like bootstrap and tailwind can reduce or eliminate the need to write CSS explicitly. Some tools like Sass extend CSS. They all generally produce regular CSS that gets read by the browser.
Specifically, the thing that exists is a regular homotopy of immersions from the standard embedding to its opposite. The "rules" aren't supposed to be self evident, they're part of a broader context in topology
The eigenvalues of a diagonal matrix are the values on the diagonal. Diagonalizable matrices' eigenvalues can be determined by diagonalizing them and looking at the entries on the diagonal.
It's interesting because it's highly counter-intuitive that such a thing is possible. It's not supposed to be useful except as an example of a false intuition, which can remind us to be careful in our reasoning.
Microsoft blocks people from downloading stuff all the time for unknowable reasons. You have to either reset your IP or go through customer support to fix it. I did the latter and they did not tell me why I was blocked in the first place.
But something has to be written on the birth certificate and social security card, and that's what everything else will expect you to use. I think just due to technical limitations (e.g. of the printer/template for those things) it wouldn't be allowed, but I dunno about legally
You're talking about a metric tensor on a pseudo-Riemannian manifold, I'm talking about a metric space. A metric in the sense of a metric space takes nonnegative real values. If you relax the condition that distinct points have nonzero distance, it's a pseudometric.