Euler was a very prolific mathematician (founder of topology I believe), and one of the other things he investigated was buckling of beams under end load, force to buckle = pi2*E*I/Leff2. I suppose you could call that Euler's formula, but usually known as Euler buckling.
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eiπ + 1 = 0 Beautiful. 5 of the most important concepts in mathematics united in one formula.
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