assuming at t0, x is 0

Tan(0)=(0)

sqrt(tan(0)) = 0

velocity = 0

the particle does not move.

Therefore X at 30 = 0.

what put me onto this was that dx/dt is not a function of T and it is very sensitive to the initial value of x. As no initial value of x is given, I assume it is zero?

If X does not start at zero, we get a problem because X increases with time until it gets to x=pi/2 when tan(x) is infinite, an instant after that, tan(x) goes negative and the sqrt becomes imaginary. So, unless x is allowed to be a complex number, it pretty much has to start, and remain, at zero.