Question

Find the Riemann sum for
f(x) = sin x
over the interval
[0, 2π],
where
x0 = 0, x1 = π/4, x2 = π/3, x3 = π, and x4 = 2π,
and where
c1 = π/6, c2 = π/3, c3 = 2π/3, and c4 = 3π/2.