Do you really think the pyramids were built without
A^2 + B^2 = C^2 ??
Probably not in this form. The Egyptians knew of the 3,4,5 right triangle, and based everything from there. They didn't use 5,12,13 right triangles, or other right triangles that were not 3,4,5.
Sort of like how this thread is going -- some people are using algebra without knowing it. The Egyptians were using the Pythagorean theorem without knowing it.