éè§
ï¼1ï¼ä½å¼¦å®ç解æ³cosa=ï¼6^2+6^2-3*36ï¼/2*6*6
=-1/2
a=120°>90°ï¼æ以为éè§ä¸è§å½¢ã
ï¼2)å¤ææ³
å¦æä¸è§å½¢ä¸ºç´è§ä¸è§å½¢ï¼ååºè¾¹é¿åº¦ä¸º6åæ ¹å·2
6åæ ¹å·2<6åæ ¹å·3,æ ¹æ®å¤§è¾¹å¯¹å¤§è§è§åï¼é¡¶è§å¤§äº90°
å æ¤è¯¥ä¸è§å½¢ä¸ºéè§ä¸è§å½¢ï¼
å¸æé纳ï¼è°¢è°¢ï¼
追é®å¨å
![](https://video.ask-data.xyz/img.php?b=https://iknow-pic.cdn.bcebos.com/77c6a7efce1b9d16467c7e67f1deb48f8c546479?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
追çå¨ï¼