Cosmologists do it in the first three minutes. Decision theorists do it optimally. Differential analysts do it in a degenerate case. Differential geometers do it on smooth contours. Differential geometers do it over and under the curves.
Functional analysts do it with compact support.
Functional analysts do it with degenerate colonels. Galois theorists do it in a field. Game theorists do it by dominance. Game theorists do it with saddle points. Geometers do it with involutions.