Fresnel Integral

[parisse]

With the latest firmware, you will get (from CAS) a symbolic answer with erf and complex numbers.
int(cos(x^2),x,0,t)
int(cos(x^2),x,0,1000);
evalf(int(cos(x^2),x,0,1000))
If you try to compute the integral numerically:
int(cos(x^2),x,0,1000.0)
the quadrature fails because the integrand is varying much too fast (especially near 1000), this is why you get a warning on the terminal, and the answer returned is a vector of 2 values corresponding to the last computed approximations.