Do the following. Estimate the area under the graph of f(x)-4 cos(x) from x 0 to x/2. (Round the answer to four decimal places.) (a) Use four approximating rectangles and right endpoints. R₁- Is your estimate an underestimate or an overestimate? underestimate ⚫ overestimate (b) Use four approximating rectangles and left endpoints. Is your estimate an underestimate or an overestimate? underestimate Ⓒ overestimate