a triangle has a total of exterior angles
Sum of angles of a triangle Angles between adjacent sides of a triangle are referred to as interior angles in Euclidean and other geometries. Exterior angles can be also defined, and the Euclidean triangle postulate can be formulated as the exterior angle theorem. One can also consider the sum of all three exterior angles, that equals to 360°[7] in the Euclidean case (as for any convex polygon), is less than 360° in the spherical case, and is greater than 360° in the hyperbolic case.
Bracket Forms include round (also called "parentheses"), square, curly (also called "braces"), and angle brackets (also called "chevrons"); and various other pairs of symbols.
Perpendicular The legs of a right triangle are perpendicular to each other.
Limit of a function (the Dirichlet function) has no limit at any x-coordinate.