Brains over calculators, part 2.

An analog clock reading 4:212014-05-22 / 2014-W21-4T16:21:47-05:00 / 0x537e6a6b

Categories: math

I recently found another calculation that I would consider reasonable for my students to perform that their calculators cannot. On my Calc II students’ final exam, I asked them to evaluate the infinite series \(\displaystyle \sum_{n = 1}^\infty \frac{4}{(n + 3)(n+5)}\). As a hint, I told them to rewrite in telescoping form using partial fractions. However, the TI-89 cannot evaluate this series. Since it’s hard to take a good photo of the calculator screen, I’ve instead included a screen shot of the TI-Nsipre CAS iPad app.

Screen shot of app, which emulates a graphing calculator. The series has been input, but instead of evaluating, the calculator returns the same series with the constant 4 factored out.