Triangle their internal angles, measured here in degrees. A triangle that has two angles with the same measure also has two sides with the same length, and therefore it is an isosceles triangle. It follows that in a triangle where all angles have the same measure, all three sides have the same length, and such a triangle is therefore equilateral. Triangles are assumed to be two-dimensional plane figures, unless the context provides otherwise (see Non-planar triangles, below). In rigorous treatments, a triangle is therefore called a "2-simplex" (see also Polytope). Elementary facts about triangles were presented by Euclid in books 1–4
What If (comics) series ran from February 1977 to October 1984. The first "What If" story was "What If Spider-Man had Joined the 'Fantastic Four'?". It presented an alternate version of events seen in "The Amazing Spider-Man" #1 (1963). "What If" #24, which is titled "What If Gwen Stacy Had Lived?" and focuses on the consequences of Spider-Man's secret identity being publicly exposed, is one of the most highly regarded "What If" stories. Following the cancellation of the series, Marvel published a one-shot "What If? Special" (June 1988) with the story "What If Iron Man Had Been a Traitor?" From July 1989 to