Mathematics · 34 visual lessons

Sequences and infinite series
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Explore integration, differential equations, series, and geometry through physical models.

Follow the real situation, derive the mathematics, and test it with interactive graphs and worked practice.

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Unit 4 · 9 lessons

Sequences and infinite series

Interactive lesson

A sequence approaches a value term by term.

Repeated approximations can settle toward a target. The index labels discrete observations rather than continuous time.

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Interactive lesson

Partial sums determine a series' value.

A repeating fractional contribution can add to a finite total. Follow the partial sums instead of only the individual contributions.

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Interactive lesson

An infinite sum can be compared with an infinite area.

A decreasing positive sequence of contributions can be bracketed by areas. The same construction also bounds the remainder.

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Interactive lesson

A known convergent sum can control a smaller one.

A complicated positive term may be bounded by a simpler power-law term. Use that inequality to decide convergence.

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Interactive lesson

A factorial can outrun an exponential.

Terms involving factorials can initially grow, yet eventually shrink rapidly. Inspect how one term compares with the next.

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Interactive lesson

A root test exposes an exponential factor.

An nth root can separate exponential growth from slower polynomial effects. Its limiting value decides most cases.

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Interactive lesson

Cancellation can produce conditional convergence.

Positive and negative contributions can settle even when the sum of their magnitudes grows without bound.

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Interactive lesson

An infinite polynomial has a convergence interval.

A finite polynomial can be evaluated anywhere, but an infinite series may represent a function only inside a specific radius.

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Interactive lesson

Match more derivatives to improve a local approximation.

An exponential response can be approximated near zero by a line, a quadratic, or a higher-degree polynomial. Compare error as you change degree.

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