Essential for deriving the casimir force is the euler-maclaurin formula that expresses the difference between a sum (needed for incorporating modes between mirrors) and an integral (needed for incorporating the modes between mirrors infinitely far apart). first describe the origin of the casimir force qualitatively, but in some detail (without relying on the euler-maclaurin formula). second make a brief study of the euler-maclaurin formula (e. g wikipedia and other websites) to get a better understanding of this important formula (you dont have to hand-in anything for this second part).