Because of the complexity of Cardano's work, and also because of the fact that accepting his method would have meant to accept the existence of numbers whose square was -1, not all the mathematicians of the time were convinced of the correctedness of Cardan's formula. Among the opposers (or at least among those who expressed some doubt) there were famous and capable mathematicians, like for example Pedro Nuñez, who was the cartographer of the king of Portugal. On the other hand, the mathematicians who tried to use Cardan's methods to discover the solution of the quintic equation were many, of course none of them succeeding. The ``by-products" of their research, though, were notable.