⑩天掌 Teaching Plan on Advanced Mathematics o f(x)dx 2 (2)求an f(x) cos ndx= o cos nrdc +ela. cos kx cos ndx +bs sin k cos ndx] tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics 2 , 2 0 =   a   =  − a f (x)dx 1 0 dx a kxdx b kxdx a k k k k cos sin 2 1 1 0    −   = −  = − = + +       (2) . n 求a  =   −  − nxdx a f x nxdx cos 2 ( )cos 0 [ cos cos sin cos ] 1     −  −  = + a kx nxdx + bk kx nxdx k k