A function f(x)f(x)f(x) is defined by f(x)=∫x2xcos(t2)dtf(x) = \int_{x}^{2x} \cos(t^2) dtf(x)=∫x2xcos(t2)dt. What is the derivative f′(x)f'(x)f′(x)?
2cos(4x2)−cos(x2)2\cos(4x^2) - \cos(x^2)2cos(4x2)−cos(x2)
cos(4x2)−cos(x2)\cos(4x^2) - \cos(x^2)cos(4x2)−cos(x2)
4xcos(4x2)−cos(x2)4x\cos(4x^2) - \cos(x^2)4xcos(4x2)−cos(x2)
2xcos(4x2)−xcos(x2)2x\cos(4x^2) - x\cos(x^2)2xcos(4x2)−xcos(x2)