ISO 216

--- https://en.wikipedia.org/wiki/Paper_size

--- https://en.wikipedia.org/wiki/ISO_216

see math notation

iso 216 paper sizes are defined to have an aspect ratio of \2/ -- 1. their dimensions can then be defined inductively as follows:

• A 0 paper has an area of 1 "m"2, and A (n:1) paper has half the area of A n paper
• B 0 paper has a width of 1 "m"2, and B (n:1) paper has half the area of B n paper

properties

B n |- A n, for all n

B-series paper sizes are defined as the geometric mean of two successive A-series paper sizes

\2/ -- 1 is the only aspect ratio that allows folding a sheet of paper in half to produce a sheet of paper of the same aspect ratio

proof let an A 0 sheet of size (L, l). then, an A 1 sheet will be of size (l, L-2). therefore, L -- l = l -- L-2 == L2-2 = l2 == L -- l = \2/ --- me

representations