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In page History of mathematics:

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Throughout the 19th century mathematics became increasingly abstract.[1] Carl Friedrich Gauss (1777–1855) epitomizes this trend.[citation needed] He did revolutionary work on functions of complex variables, in geometry, and on the convergence of series, leaving aside his many contributions to science. He also gave the first satisfactory proofs of the fundamental theorem of algebra and of the quadratic reciprocity law.[citation needed]