We can evaluate the integral using the following steps:
1. Recall that the integral of sin(x) with respect to x is -cos(x) + C, where C is the constant of integration.
2. Using this formula, we can integrate sin(x) between the limits of integration π/2 and 0:
∫π/20 sin(x) dx = [-cos(x)]π/20 = (-cos(π/2)) - (-cos(0)) = (-0) - (-1) = 1
3. Therefore, the value of the integral is 1.
So the correct answer is 3.