Ormewood is correct that later revisions by someone (to put all wind considerations into one section) caused a loss of continuity. I was the original author of the section "Shape of The Tower" in March of 2007, so I know that the orphaned sentences answer the question: What mathmatical calculation was Eiffel referring to? I tried to edit the article, but found it is now semi-protected owing to excessive vandalism. I propose that an autoconfirmed user revise the entire paragraph as follows:
In search of what mathmatical calculation Eiffel referred to, researchers have found that Eiffel used empirical and graphical methods accounting for the effects of wind rather than a specific mathmatical formula. Careful examination of the tower shows a basically exponential shape; actually two different exponentials, the lower section overdesigned to ensure resistance to wind forces. Several mathmatical explanations have been proposed over the years; the most recent is described as a nonlinear integral equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point. As a demonstration of the tower's effectiveness in wind resistance, it sways only 6–7 cm (2–3 in) in the wind.

I would be happy for any assistance in further editing or rewriting.