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Excellent, Frank, and Thank you ! :-)

Since I earlier submitted :

" I would then surmise that this would happen at a Latitude where the relative lengths of both 1° of Latitude and 1° of Longitude would exactly match the same ratio observed on a Sphere "

and :

provided that we are authorized by the Mathematician on duty to rely onto only your first published terms of such Ellipsoids infinite series, solving for:

dLon/dLat (Sphere) = dLon/dLat (Ellipsoid)

boils down to solving for:

ε (1 + cos 2L ) = 0

with immediate solutions as:

ε = 0 , i.e. a Sphere itself (trivial case). And :

cos 2L = -1, yielding 2L = +/- 180°, hence L = +/- 90° in the case of an Ellipsoid

The above is a mathematical demonstration, while Page 2 only partially verifies this mathematical result albeit probably in some much more instructive manner .

Therefore no need to publish this partial verification anywhere else then, and Thanks to u 2 David for your kind comments.

Kermit