Abstract: A difficult problem,i. e.,applicative treatment for the result in statistical physics course is discussed. These applications considered here are the Stirling＇s formula; the summation being replaced by an integration; the series expansion at high and low temperatures,respectively. Their mathematical base and physical use are analyzed and we compare the precision of various results by using numerical calculation.

Key words: Stirling＇s formula, summation replaced by an integration, series expansion, diatomic molecule