## The gallery

The gallery is the engine room of the pyramid where the main calculations required to calibrate the geometry are
performed. It will be analysed over the coming pages, and because the design is highly complex it is worth summarising
the architectural concept of the gallery that will be discovered, which is quite straight forward, before embarking on the analysis.

### The gallery's architecture system

- The gallery groove angle is linked to the gallery floor angle
- The gallery floor angle is linked to the gallery roof angle
- The mathematics that links these angles is contained in the gallery end walls

### The gallery roof

The roof of the gallery is not continuous straight line, but is made up of a series of ratcheted stones as can be seen by
zooming in
on an arbitrarily selected area of the roof. The ratchets themselves are cut at an angle that is perpendicular
to the slope line of the roof stones, and are not vertical.

The reason for the roof being built in this way is that a nominal 'test' angle of the roof of the gallery is defined from a right
angled triangle that conforms to the roof's architecture.
If you
display the triangle
you can see that it is a primitive right angled triangle with a hypotenuse of 221 and a side length of 200, the
units of length being irrelevant.
These values have already been used for the cubit to radian ratios seen earlier (page C5); 200 in the gallery and lower northern shaft
and 221 in the lower southern shaft and the value of 221 was so important that the architects painted it in red
numerals behind the door at the end of the lower southern shaft.

This primitive triangle is essential for understanding the gallery and calibrating the architectural design because it
defines the 'test' roof angle of the gallery as arcCosine(200/221) = 25.17976°. This angle can be calculated to as many decimal places
of accuracy as we need, which is the very reason for it being defined in this way.

The triangle is also used in the gallery end walls and floor construction in two specifically sized formats where it is scaled
so that the hypotenuse of the triangle is 0.221 and .0221 cubits long and the other integer length
side is 0.2 and 0.02 cubits long. These triangles have the following dimensions, shown in cubits, metric and inches so that
they can be compared to Petrie's original survey dimensions if desired.

___________________

Last edited: 13^{th} September 2019

Last code/graphics edit: 29^{th} March 2021