Fresnel Integrals S(x) and C(x) are two transcendal functions named after Augustin-Jean Fresnel that are used in Optics and are closely related to the error function (erf). They arise in the description of near-field Fresnel diffraction phenomena and are defined through the following integral representations:
S(x) = I(sin(t^2)dt):0-x, C(x) = I(cos(t^2)dt):0-x
The simultaneous parametric plot of S(x) and C(x) is the Euler Spiral