The figure below illustrates both integrals. {{CMD_32}} {{ENV_33}} {{ENV_34}} {{CMD_35}} The two shaded areas in the figure, {{MATH_36}} and {{MATH_37}}, appear to be equal, and this confirms what was established by computation before. Therefore, whenever we are faced with a problem of evaluating a difficult integral, we try to replace it with a simpler one, as long as both integrals represent the same net area.