Explorando o uso da janela CAS do GeoGebra para determinar períodos de dízimas periódicas no ensino de matemática

The article explores the use of the GeoGebra CAS view to determine the period length of repeating decimals, a relevant topic for mathematics education that can be enhanced through educational technologies. The text presents the mathematical concepts involved in determining the period of infinite, periodic rational numbers, particularly applying Fermat's Little Theorem to identify the period length of rational numbers with prime denominators. Specific commands within the GeoGebra CAS Window are highlighted, enabling students to explore numerical and symbolic operations, which can encourage the formulation of conjectures and problem-solving. The study concludes that the CAS Window is an effective tool for investigative learning in mathematics, though it has limitations in certain contexts.