>>306094654
back on my PC:

So the length of a side of the Great pyramid of Gizeh is 230.34meters.
To get the inner circle, we just have to multiply this diameter by pi.
so let's say the inner circumfrence gets symbol 'A'
A=pi*230.34m
A=723.63445182787297454748527690459542
====================================

The outer circle is a bit "harder" (basic trigonometry), we use the theorem of pythagoras:
c²=a²+b²
where c is the hypotenuse and a and b are the "legs"
now, as the pyramid is a square in top-down view, we plug 230.34 in for a and b respectively which yields:
c²=(230.34²)+(230.34²)
result is c²=106113.0312
now to get the length we take the square root:
c=sqrt(c²)
c=325.74995195701871354098098073446185

Now that we have c, we can calculate the outer circles circumfrence:
B=c*pi
B=1023.37365597539808133763802725057271
=====================================

Now subtract A from B:
C=B-A
C=1023.37365597539808133763802725057271-723.63445182787297454748527690459542
C=299.73920414752510679015275034597729
====================================

lightspeed determined via electric and magnetic constants (look up lightspeed):
D=299792458m/s
then if we move the decimal place to match, we have a value of
C=299739204.14752510679015275034597729m/s
now divide C by D:
C/D=299739204.14752510679015275034597729/299792458
C/D=0.99982236426883396376219961592888
= 99.9822...% accuracy