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An equation that relates the product of the mass density and the velocity of a fluid to the divergence of the stress tensor is called this man's "momentum equation." A theorem named for him states that the integral of a holomorphic function over a closed loop is equal to zero, and he also co-names a pair of equations that must be satisfied by the real and imaginary parts of a holomorphic function. In addition, he co-names a relation which states that the inner product of two vectors is less than or equal to the product of their norms, of which the triangle inequality is a special case. For 10 points, identify this mathematician who lends his name to an inequality along with Hermann Schwarz. 
An equation that relates the product of the mass density and the velocity of a fluid to the divergence of the stress tensor is called this man's "momentum equation.
Augustin Louis {Cauchy}