Why is 1:√2 the only aspect ratio that remains the same when it is ‘folded in half’ (hence the usage in paper dimensions)

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1:2 becomes 1:1 or 1:4 depending on folding axis, etc

In: 10

3 Answers

Anonymous 0 Comments

Just simple Math: (Maybe not for a five years old)

Original sheet: Width: W and Height: H

Folded sheet: New width: w = H and new height: h = W/2

Requested: H/W = h/w

leads to: H/W = (W/2)/H

Multiply both side by (H/W): H/W * H/W = 1/2

Then: H/W = 1/√2

Anonymous 0 Comments

Take a piece of paper with an aspect ratio of 1:√2. If you fold it in half along the long axis, then its aspect ratio becomes 1:(√2)/2. Now, to see that this is the same aspect ratio, scale both sides up by √2. Then the aspect ratio would be √2:(√2*√2)/2. √2*√2 = 2, that’s what √2 means, so the aspect ratio is √2:2/2 = √2:1. This is the same aspect ratio as before, just the other way round.

Anonymous 0 Comments

The basic math excercise was already explained before in other comments, so i won’t repeat the steps.

I would like to add one thing: the math results at the end to this formula

>(a/b)^2 = constant

This equation always has *1 and only 1 positive solution*. This means that whatever folding proportion you choose, only 1 aspect ratio will ever work to satisfy the equation.

If you choose 1/2 (to fold in half) the number turns out to be 1/sqrt(2). The “cool mathy thing” is the fact that **only one aspect ratio** will ever work, given a folding pattern, and no one aspect ratio will ever work for more than one folding pattern.
1/sqrt(2) has nothing special “per se”, it just solves the equation.