Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In geometry, a decagonal bipyramid is one of the infinite set of bipyramids, dual to the infinite prisms. If a decagonal bipyramid is to be face-transitive, all faces must be isosceles triangles. However, there is a rather odd-looking version of the decaagonal bipyramid with each of the faces congruent having a right scalene triangle as the shape of the faces.