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Origami (折り紙)
Analyzing folding on a square paper
A fold on a square paper
A fold on a rectangular paper
A fold on an A4 paper
Folding two opposite vertices of a square paper
Make a special triangle with a square paper
Fold to make a bisector of a triangle
Distinguishing bisectors of a triangle
Mon-kiri (紋切り)
Making shapes with reflectional symmetry
Make a fold on half of a square paper, the first step for folding a regular hexagon or regular pentagon. The methods are based on folding a 60 deg angle at center (for hexagon) and an approximate of 36 or 72 deg angle (for pentagon).
These methods are explained in:
1. Unfolding Mathematics with Unit Origami by Betsy Franco, Activity 6 & 8.
2. Amazing Origami by Kunihiko Kasahara, pp.18 & 28-29
3. The Regular Pentagon by Jim Loy (http://www.jimloy.com/geometry/pentagon.htm) , addendum #2
Here are photos of some examples of mon-kiri.
Examples 1
Examples 2
References
Olson, A.T. (1975) Mathematics Through Paper Folding. Reston, Va.: National Council of Teachers of Mathematics.
http://www.vidyaonline.net/arvindgupta/paperfolding.pdf