Questions tagged [fresnel-integrals]

Questions on the Fresnel integrals.

Different normalizations are done for the Fresnel integrals. One normalization is

$$\begin{align*} S(x)&=\int_0^x \sin(t^2)\,\mathrm dt \\ C(x)&=\int_0^x \cos(t^2)\,\mathrm dt \end{align*}$$

and a different normalization is

$$\begin{align*} S(x)&=\int_0^x \sin\frac{\pi t^2}{2}\mathrm dt \\ C(x)&=\int_0^x \cos\frac{\pi t^2}{2}\mathrm dt \end{align*}$$

Check your reference to see which normalization is being used.

98 questions
44
votes
5 answers

Proof only by transformation that : $ \int_0^\infty \cos(x^2) dx = \int_0^\infty \sin(x^2) dx $

This was a question in our exam and I did not know which change of variables or trick to apply How to show by inspection ( change of variables or whatever trick ) that $$ \int_0^\infty \cos(x^2) dx = \int_0^\infty \sin(x^2) dx \tag{I}…
36
votes
4 answers

An integral involving Fresnel integrals $\int_0^\infty \left(\left(2\ S(x)-1\right)^2+\left(2\ C(x)-1\right)^2\right)^2 x\ \mathrm dx,$

I need to calculate the following integral: $$\int_0^\infty \left(\left(2\ S(x)-1\right)^2+\left(2\ C(x)-1\right)^2\right)^2 x\ \mathrm dx,$$ where $$S(x)=\int_0^x\sin\frac{\pi z^2}{2}\mathrm dz,$$ $$C(x)=\int_0^x\cos\frac{\pi z^2}{2}\mathrm…
12
votes
1 answer

Need help with $\int_0^\infty\left(\pi\,x+\frac{S(x)\cos\frac{\pi x^2}2-C(x)\sin\frac{\pi x^2}2}{S(x)^2+C(x)^2}\right)dx$

Let $$I=\int_0^\infty\left(\pi\,x+\frac{S(x)\cos\frac{\pi x^2}2-C(x)\sin\frac{\pi x^2}2}{S(x)^2+C(x)^2}\right)dx,\tag1$$ where $$S(x)=-\frac12+\int_0^x\sin\frac{\pi t^2}2dt,\tag2$$ $$C(s)=-\frac12+\int_0^x\cos\frac{\pi t^2}2dt\tag3$$ are shifted…
9
votes
2 answers

Trig Fresnel Integral

$$\int_{0}^{\infty }\sin(x^{2})dx$$ I'm confused with this integral because the square is on the x, not the whole function. How can I integrate it? Thank you. I have not done complex analysis (only real analysis as I am a high school student) so how…
9
votes
1 answer

How to show that $\int_0^1 \sin \pi t ~ \left( \zeta (\frac12, \frac{t}{2})-\zeta (\frac12, \frac{t+1}{2}) \right) dt=1$?

I've been trying to prove Fresnel integrals by real methods and encountered an interesting problem. Let's start with the known result: $$\int_0^\infty \sin y^2 dy = \sqrt{\frac{\pi}{8}}$$ Can we prove it without complex methods? I have tried to do…
9
votes
6 answers

Compute the value of Fresnel's Integral

So, my teacher wants us to compute the value of the Fresnel integral: $$\int_0^\infty\cos(x^2)dx=\sqrt{\frac{\pi}{8}}$$ The problem is that we cannot use complex analysis to prove that and we should do that using the Euler…
7
votes
2 answers

Are Complex Substitutions Legal in Integration?

This question has been irritating me for awhile so I thought I'd ask here. Are complex substitutions in integration okay? Can the following substitution used to evaluate the Fresnel integrals: $$\int_{0}^{\infty} \sin x^2\, dx=\operatorname…
6
votes
1 answer

Quadratic-trigonometric integral -- part 2

Problem I need to compute the following integral \begin{equation*}\int_{t_\text{s}}^{t_\text{e}} \cos(a+b\tau+c\tau^2)\text{ d}\tau\end{equation*} where $t_{\text{s}}0$ are given parameters. Remark Actually, thanks to the…
6
votes
1 answer

Definite integral involving Fresnel integrals

I am seeking to evaluate $\int_0^{\infty} f(x)/x^2 \, dx$ with $f(x)=1-\sqrt{\pi/6} \left(\cos (x) C\left(\sqrt{\frac{6 x}{\pi }} \right)+S\left(\sqrt{\frac{6 x}{\pi }} \right) \sin (x)\right)/\sqrt{x}$. $C(x)$ and $S(x)$ are the Fresnel…
6
votes
1 answer

Connect two curves with Euler spiral segment

Image of situation: http://upload.wikimedia.org/wikipedia/commons/5/54/Easement_curve.svg Let's say we have a straight line (blue) and a circular arc (green). My goal is to connect these two curves with segment of Euler spiral (red) in such manner…
5
votes
2 answers

Does this integral, related to the Fresnel integrals, have a name or a known solution?

I've been working on a problem in light propagation, where the crux of a derivation boils down to understanding the following integral: $$\int_{-x_0}^{x_0} e^{i \alpha \sqrt{1-x^2}} dx, $$ with the square root taking the positive imaginary branch…
5
votes
2 answers

Can we evaluate the Fresnel integral of a quadratic in general using real methods?

After tackling about the Fresnel integral in the post, I want go further with its quadratic as $$ \int_{-\infty}^{\infty} \sin \left(a x^2+b x+c\right) d x $$ where $a,b $ and $c$ are real. Starting with easy, we first consider the case…
5
votes
0 answers

Fresnel Integral Proof (without rigorous complex analysis)

I’d like to present my dodgy proof of the Fresnel Integrals, which I wrote before I knew anything about complex analysis. It takes some… liberties; yet, it still managed to produce the right value for both integrals, so I thought it might be worth…
Mailbox
  • 941
5
votes
2 answers

Sum of squared Fresnel sine integral

I'm trying to find the following sum: $$ \sum_{n=0}^{\infty} \frac{S\left(\sqrt{2n}\right)^2}{n^3}$$ where $S(n)$ is the fresnel sine integral, however, I think I made a mistake somewhere. To start, I considered using parseval's identity: $$…
5
votes
1 answer

Proving that $\int_{0}^{+\infty}e^{ix^n}\text{d}x=\Gamma\left(1+\frac{1}{n}\right)e^{i\pi/2n}$

I've shown that for all $p \in \mathbb{R}^{*+}$ $$\int_{0}^{+\infty}e^{-x^p}\text{d}x=\Gamma\left(1+\frac{1}{p}\right)$$ And I want to show that $$ \int_{0}^{+\infty}e^{ix^n}\text{d}x=\Gamma\left(1+\frac{1}{n}\right)e^{i\pi/2n} $$ Is that possible…
Atmos
  • 7,455
1
2 3 4 5 6 7