Cauchy (1821) kekeh saking tes konvergensi sane ketat, ia nyinahang wantah yening kalih deret konvergen, produk ipun durung sakadi kenten, lan antuk ia ngawitin patemon kriteria sane efektif.
Cauchy (1821) insisted on strict tests of convergence; he showed that if two series are convergent their product is not necessarily so, and with him begins the discovery of effective criteria.