# Fresnel cosine integral

For functions involving angles (trigonometric functions, inverse trigonometric functions, etc.) we follow the convention that all angles are measured in radians. Thus, for instance, the angle of $90\,^\circ$ is measured as $\pi/2$.
The Fresnel cosine integral, which we denote here by $C$, is defined as a definite integral of the cos(x^2) function:
$C(x) = \int_0^x \cos(t^2) \, dt$