You should also not dicount the documented evidence that some of the later-period phharoahs liked to "rennovate" older temples & such...Usually
erasing the names of the earlier pharoahs who took credit for the original construction & inscribing their own names as a replacement. Also, there
have been at least 3 occasions (according to my memory of the history of Egypt) when pharoahs had taken tomb-contents away from the original tombs,
using the contents either for their own tombs or to enhance the royal treasury & in some occasions, reusing the original tombs for their own
purposes.
IMO, based upon my own studies of Egypt, they did indeed build the Pyramids of Giza (Although I still have no final opinion on the Sphinx just yet).
However, it's been made obvious to me that they also had a much more complete working knowledge about the Earth than most archeologists would be
willing to give them credit for.
As a bit of contradiction though, most of their common records indicate that they were more likely to use "rule of thumb" matematics when concerned
with everday use, such as measuring tribute or dividing fields into organized sections...Basically, the most common & widley used calculations were
practical for the sake of simplicity.
However, such measurements as could be found in the Great Pyramid indicates that the Egyptians knew details about the structure of the Earth with such
precision that could only be matched with modern technology, such as the circumference of the Earth, the measurements of longitude & latitude, the
amount of "equatorial bulge" in the Earth, and even the distance from the (true) North Pole to the center fo the core.
Still, who knows how much knowledge was lost with the distruction of the Alexandrian Library? Pharonic Law during the Ptolemic periods allowed
Egyptian scholars to copy *every* book or parchment that crossed into the country's borders...Every scrap of knowledge that the Egyptians had or
could get a hold of were destined to wind up in the Library (or the attached Museum).
Damn the religious fanatics that invaded Egypt & decided to destroy everything that they didn't agree with!