a) The rectangles in the graph below illustrate a Riemann sum for $\displaystyle f(x) = 2 \sin x$ on the interval $[0, \pi]$.
The value of this Riemann sum is .

 Left endpoint Riemann sum for $y = 2 \sin x$ on $\lbrack 0, \pi \rbrack$

b) The rectangles in the graph below illustrate a Riemann sum for $\displaystyle f(x) = 2 \sin x$ on the interval $\lbrack 0, \pi \rbrack$.
The value of this Riemann sum is .

 Right endpoint Riemann sum for $y = 2 \sin x$ on $\lbrack 0, \pi \rbrack$