Lemma: Riemann Integral of a Product of Continuously Differentiable Functions with Sine

Let $[a,b]$ be a closed real interval and let $f:[a,b]\to\mathbb R$ be a continuously differentiable function. For $y\in\mathbb R,$ we define the Riemann integral. $$F(y):=\int_{a}^{b}f(x)\sin(yx)dx.$$ Then the limit of $F(y)$ tends to $0$ as $y$ tends to infinity. Formally, then $$\lim_{|y|\to\infty}F(y)=0.$$

Proofs: 1


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References

Bibliography

  1. Forster Otto: "Analysis 1, Differential- und Integralrechnung einer Veränderlichen", Vieweg Studium, 1983