设两平é¢çæ³åéåå«ä¸ºn1,n2.设äºé¢è§çå¹³é¢è§ä¸ºÎ±ã
åcosα=± (n1•n2) / (|n1||n2|)
åæ£å·è¿æ¯è´å·åå³äºè¿ä¸ªäºé¢è§æ¯éè§è¿æ¯éè§ã
å¦ä½å¤ææ¯éè§è¿æ¯éè§å¢ï¼æ两ç§æ¹æ³ï¼
1ãæ ¹æ®é¢ç®ï¼çåºæ¯éè§æéè§ï¼æ¤æ¶ç¬¦å·åæ£æåè´ï¼
2ãæ ¹æ®ä¸¤æ³åéçæ¹åæ¥å¤æï¼äºé¢è§æ空é´åæ两é¨åãå½ä¸¤æ³åéç©¿è¶å¹³é¢åï¼å¦ææ¹åæåå侧ï¼ååè´å·ï¼å¦ææ¹åæåå¼ä¾§ï¼ ååæ£å·ã