0 <= x <= π/2,
∫_{0}^{x}f(t)dt = ∫_{0}^{x}sin(t)dt = 1 - cos(x)
π/2 ≤ x ≤ π,
∫_{0}^{x}f(t)dt = ∫_{0}^{π/2}f(t)dt + ∫_{π/2}^{x}f(t)dt
= ∫_{0}^{π/2}sin(t)dt + ∫_{π/2}^{x}dt/2
= 1 + (x - π/2)/2