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folding a paper triangle to get surface of a regular unit tetradragon

Source: III Soros Olympiad 1996-97 R2 11. 5 https://artofproblemsolving.com/community/c2416727_soros_olympiad_in_mathematics

May 31, 2024
geometrycombinatorial geometry

Problem Statement

Prove that this triangle cut out of paper can be folded so that the surface of a regular unit tetradragon (i.e., a triangular pyramid, all edges of which are equal to 11) is obtained if: a) this triangle is isosceles, the lateral sides are equal to 22 , the angle between them is 120o120^o, b) two sides of this triangle are equal to 22 and 232\sqrt3, the angle between them is 150o150^o.