ÒÑÖªÒ»¸öÒÔ 2 ΪÖÜÆÚµÄÖÜÆÚº¯Êý f.
ÄãµÄÈÎÎñÊÇÕÒ³öÕâ¸öº¯ÊýµÄ
Fourier ¼¶ÊýÕ¹¿ª
µÄµÚÒ»ÏîϵÊý.
Äã¿ÉÒÔ×÷¶à´Î³¢ÊÔ. ÿ´Î³¢ÊÔ¶¼¿ÉÒÔ¿´µ½ÄãµÄ``Õ¹¿ªÊ½'' g ÒÔ¼°º¯Êý f µÄÇúÏß. È»ºóÄã¿ÉÒÔÐÞ¸ÄÄãµÄ»Ø´ð, ʹµÃÁ½ÌõÇúÏß¾¡¿ÉÄܽӽü. ÓàÏî f-g µÄÇúÏßÒ²±»»³ö, ʹÄãÄÜ¿´µ½Îó²î.