Hi Mark,

It is a shame we of western world have a tendency to complicate simplicity. It seems we are still unable to think in the simple terms of the Ancient Egyptians. Quite simply the lower slope of Bent pyramid is a 10 rise : 7 run base angle multiplied by 2/3 = 20/21 upper rise run.

Yields our values as follows:
A 4 9/10 seked, a cotan:7/10 = 34º 59' 31.27" - 90º = tan:10/7 = 55º 0' 28.73" Lower slope of Bent Pyramid.
A 7 7/20 seked, a cotan:21/20 = 46º 23' 49.85" - 90º = tan:20/21 43º 36' 10.15" Upper slope of Bent Pyramid.

Petrie's assessment of a 20:21:29 triangle for the Red Pyramid would seem to be correct. Giving the Bent Pyramid upper and Red Pyramid equal slope.

My opinion is the Bent Pyramid's 360 cubits is correct, having a 6/7 ratio to the 420 cubits of Red Pyramid.

Angles are our thing, the seked (cotangent) was the method of the Ancient Egyptians. From my perspective continuing to work in angles only confuses their intent. Instead of employing our methods maybe we should be trying to understand the simplicity of their mindset and methodologies. Simplicity is the Key.

Just my 2 cents.

Regards,
Jacob