# Scaled Polydom Tetrads

## Introduction

In plane geometry, a *tetrad* is an arrangement of four congruent
shapes in which each borders the other three.
See Polyform Tetrads.
At his website Atlantis, Dr. Karl Scherer introduced *similar*
or *scaled tetrads.*
These are arrangements of four *similar*
shapes in which each borders the
other three.
In general, scaled tetrads are easier to find that standard tetrads.

A *polydom* is a polyform whose cells are 2×1 right
triangles.
I exclude polydoms that contain a *kite didom*:

For kiteless polydoms, the orthogonal edges must conform to the square grid.

Here I show the smallest known scaled
tetrads for polydoms with 2, 3, or 4 cells,
keeping to the grid and
using scale factors that are integers or integer multiples of √5.
If you find a smaller solution or solve an unsolved case, please write.

## Didoms

The tetrad on the left was found by
Abaroth.

## Tridoms

## Tetradoms

Last revised 2018-11-15.

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Col. George Sicherman
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