Which integral expression represents the area of the region enclosed by the curves y = cos(x), y = sin(x), x = 0, x = pi/2?
A) ∫(0 to pi/2) sin(x) - cos(x) dx
B) ∫(0 to pi/2) cos(x) - sin(x) dx
C) ∫(0 to 1) sin(x) - cos(x) dx
D) ∫(0 to 1) cos(x) - sin(x) dx