Dislosure: I'm not directly from the fields of the Sciences Of Angles And Ambiguously Crossing Lines nor I've every seen or used this symbol before. However to me it's, pretty evidently, supposed to be a "no right angle" symbol.
(A) It's in the math section,
(B) it's with angles,
(C) the thunderbolt ↯ is commonly used for "not" or more specifically for dis-proof in this area and
(D) at least by my 30 s internet search on a mobile phone I couldn't find any other "no-angle" or "no-right-angle" symbol.
Someone could argue that usually you use a simple strike through as like as in ≠ (unequal), ∉ (not-element-of) or ∅ (empty set) but I would say it was chosen to avoid confusion in this case. The angle itself (without the "no/not") consists of only to orthogonal lines so it would be kinda complicated to "strike it though" in any direction without ambiguity that would resemble a triangle, a fork or whatnot.
(A) It's in the math section, (B) it's with angles, (C) the thunderbolt ↯ is commonly used for "not" or more specifically for dis-proof in this area and
(D) at least by my 30 s internet search on a mobile phone I couldn't find any other "no-angle" or "no-right-angle" symbol.
Someone could argue that usually you use a simple strike through as like as in ≠ (unequal), ∉ (not-element-of) or ∅ (empty set) but I would say it was chosen to avoid confusion in this case. The angle itself (without the "no/not") consists of only to orthogonal lines so it would be kinda complicated to "strike it though" in any direction without ambiguity that would resemble a triangle, a fork or whatnot.
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