Classroom notes: Summing sequences having mixed signs

• Main Authors: Fay, TH, Walls, GL
• Format: Others
• Language: en
• Published: International Journal of Mathematical Education in Science and Technology 2003
• Subjects: Dirichlet’s Test; Fourier series
• Online Access: http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001986

Summary A result is discussed which permits the summing of series whose terms have more complicated sign patterns than simply alternating plus and minus. The Alternating Series Test, commonly taught in beginning calculus courses, is a corollary. This result, which is not difficult to prove, widens the series summable by beginning students and paves the way for understanding more advanced questions such as convergence of Fourier series. An elementary exposition is given of Dirichlet’s Test for the convergence of a series and an elementary example suitable for a beginning calculus class and a more advanced example involving a Fourier series which is appropriate for an advanced calculus class are provided. Finally, two examples are discussed for which Dirichlet’s Test does not apply and a general procedure is given for deciding the convergence or divergence of these and similar examples.