Exercise 793Calculus › Single-variable calculus › Series › Convergence testsL1Added 2 Nov 2026
Two alternating series with logarithms
#alternating series test#monotonicity#conditional convergence
Statement
Study the convergence, absolute and conditional, of
Hint
Check the three hypotheses of the alternating series test. For the second, study .
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Solution
First series. is positive, decreasing (as increases) and tends to : the series converges. Since we have , so diverges: the convergence is conditional.
Second series. Let . Then for , so is decreasing, and it tends to . The series converges. Since for , the series of absolute values diverges: conditional convergence.
Remark. The alternating series test requires *eventual* monotonicity only: the first terms (here ) do not matter.