The term 'flexagon' is used in geometry to indicate flat models that are created when someone folds strips of paper. These flat models are often called the most fascinating geometric toys as you flex (or fold) them in a number of specific ways to reveal more faces other than the initial two.
3
2
1
4
18
19
15
16
Using Tuckerman reverse
Using Arthur reverse
Using flexagon reverse
Opening the flexagon
Isoscele
Right angle
Equilateral
Scalene
Converting the triangle to right angle
Converting the triangle to equilateral
Converting the triangle to scalene
Converting the triangle to square
Hexahexaflexagon
Hexaflexagon
Tritetraaflexagon
Octaflexagon
72-57-51
72-54-54
72-53-55
72-58-50
By multiplying its triangles
By dividing its triangles
By adding more squares
By subtracting half of its squares
Planar
Non-planar
Close
Open
Heptaflexagon
Hexaflexagon
Tetraflexagon
Hexahexaflexagon