Isosceles triangle is acute, right or obtuse depends only on the angle at its apex. In Euclidean geometry, the base angles cannot be obtuse (greater than 90°) or right (equal to 90°) because their measures would sum to at least 180°, the total of all angles in any Euclidean triangle. Since a triangle is obtuse or right if and only if one of its angles is obtuse or right, respectively, an isosceles triangle is obtuse, right or acute if and only if its apex angle is respectively obtuse, right or acute. In Edwin Abbott's book "Flatland", this classification of shapes was used
Many-angled ones a result, when they manifest in our universe they appear as disconnected floating body parts of some larger beast that is complete in the higher dimension (similar to how a three dimensional being would appear in flatland as its parts pass through the plane of that two-dimensional world). More recently, they have appeared in books by British authors or comics and video games from British comics writers who have worked for "2000 AD". The many-angled ones were mentioned in Charles Stross's "The Atrocity Archives". This work features the usual appearances by "nameless horrors of the abyss," which may or may