Sometimes it helps to think about the most basic examples. Consider {{MATH_10}} We know (by geometry) that this computes the area of a {{MATH_11}} rectangle which equals {{MATH_12}}. On the other hand, if we consider the accumulation function {{MATH_13}} we see that {{MATH_14}} {{CMD_15}} What is {{MATH_16}}? {{CMD_17}} {{MATH_18}} {{CMD_19}} {{CMD_20}}