the area in the first quadrant bounded by the curves with parametric equations x=2atan(\theta) and y=2acos^2(\theta), and the lines x=0 and x=2a, is equal to

(A) \pi a^2

(B) 2 \pi a^2

(C) \frac{\pi a}{4}

(D) \frac{\pi a}{2}

(E) none of these