biangle

From bi- +‎ angle.

• IPA^(key): /ˈbaɪˌæŋɡəl/

biangle

1. A digon or bigon; a two-sided shape (especially in non-Euclidean geometry)
   • 1895, W. Burnside, “Kinematics of Non-Euclidean Space”, in Proceedings of the Edinburgh Mathematical Society‎, page 46:

     If n planes be drawn through any axis of the right-vector, each of which makes angles π/n with the planes on either side of it, the whole of space is divided into n congruent figures which may be called biangles, the space between any two adjacent planes being easily seen to be continuous with the vertically opposite space between them.

   • 1912, Proceedings of the Edinburgh Mathematical Society‎, Scottish Academic Press, page 35:

     Then the right biangle CABD and the oblique biangle CPND are equivalent since the triangles API and BNI are congruent.

   • 2012 December 6, Gerold Prauss, “Kant and the Straight Biangle”, in Enno Rudolph; Ion-Olimpiu Stamatescu, editors, Philosophy, Mathematics and Modern Physics: A Dialogue‎, page 228:

     It is therefore natural to consider whether precisely this concept of a straight line, with which Kant¹¹ too was familiar, is the reason why Kant in the one passage says that the concept of a straight biangle is free of contradiction.

• digon, bigon, diangle