Pretty easy trig. question

Hi I've already posted this question up although its actually getting pretty urgent that I finish it because its due very soon so could someone please help me. Its pretty easy but for some reason I just can't think straight today

Find the gradient of the tangent to the curve y = x sin x^2 at the point where x = π/3

I've alreaf '(x) = sinx^2 + x(2x cos x^2)dy done the first bit and found the gradient which is:

f '(x) = sinx^2 + x(2x cos x^2)

but for some strange reason I'm real confused about where to substitute x = ** π/3 **because I see a lot of x's there but I'm not too sure on which ones I should sub this in for. I know that this should be very easy but I just can't think straight today >_<