A Sixth Platonic solid?
[1] Wouldn't gluing a tetrahedron's one triangle to a another tetrahedron's triangle make a platonic solid ? See the picture to see clearly what I mean. Tetrahedron stacked one on each makes an another solid with $6$ faces, $5$ vertices and $9$ edges.
3 Answers
No: two of the vertices would have three edges while three vertices would have four edges
You are describing a triangular bipyramid
No. By definition a Platonic solid has the same number of faces meeting at each vertex. Your solid has three faces meeting at each of two vertices and four faces meeting at each of the other three vertices.
You can also work with the angles: Along any of the edges where the tetrahedrons are spliced together, there will be a planar angle of $120^\circ$, whereas the planar angles on each tetrahedron are $60^\circ$. Since these angles differ, the solid is not regular.
