Math 2.0

definition

Conditional convergence

Definition

Let (an)(a_n) be a real sequence. The series ∑an\sum a_n converges conditionally if ∑an\sum a_n converges and ∑∣an∣\sum |a_n| diverges.

Remarks

So a convergent series converges either absolutely or conditionally, and not both. The alternating harmonic series converges conditionally. By the Riemann rearrangement theorem, the terms of a conditionally convergent series can be reordered to give any real sum.

Explanations

L1 human

A conditionally convergent series converges only because its positive and negative terms cancel. The positive terms alone add up to +∞+\infty, and the negative terms alone add up to −∞-\infty.

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  1. Sequence definition
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  8. Absolute convergence definition
  9. Conditional convergence definition

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Sources

  1. Web https://en.wikipedia.org/wiki/Conditional_convergence, Definition