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Counterexample

Is this true?

Pointwise convergence implies convergence of the integrals

No — it is false.

The counterexample

fn=n⋅1(0,1/n)f_{n} = n\cdot1_{(0,1/n)} on [0,1]

Why it fails

fn→0f_{n} \to 0 pointwise but ∫fn=1\int{}f_{n} = 1 always. Domination or monotonicity is essential.

Go deeper· Explained in full in MCT, Fatou and dominated convergence· Asked in CSIR NET June 2025· From Lebesgue Measure and Integration › Lebesgue integral, MCT, DCT, Fatou

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