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It's used in german mathematics education (secondary level), either to mark a contradiction in a proof or more generally to mark an erroneous statement.
by maze-le 4y ago
It's used in german mathematics education (secondary level), either to mark a contradiction in a proof or more generally to mark an erroneous statement.
- ruuda 4y agoAlso in Dutch universities to mark a contradiction, especially in a proof by contradiction.
- dirkt 4y agoBut I have never seen it to mark negation of a condition, that's usually done with a slash (as in ≠ ≮ ≯ ≰ ≱ ≴ ≵ ⊄ ⊅ ⊈ ⊉ ⊊ ⊋ ∉ ∌ ∄ ∦, you get the idea). So for "not a right angle" I'd have expected a "right angle" symbol with a slash through it.
- r0uv3n 4y agoBut how would you position the slash to get a somewhat easy to decipher symbol? To me, the right angle symbol seems to lend itself more to this unorthodox negation through the contradiction symbol than to negation through the normal slash.
- maze-le 4y agoFunny enough, I've only seen it at the Gymnasium (secondary level) and not in the University a few years later -- then indeed the usual symbols were the 'slashed' relations like you've described, or the bottom symbol: ⊥ in logic. Maybe it's an idiosyncrasy of a certain subset of math teachers.
- deleted 4y ago[deleted]