1ï¼å»¶é¿CP交A1C1äºDï¼è¿æ¥MDãB1D
ç±AC//A1C1ï¼C1D/AC=C1P/AP=1/2ï¼å¾C1D=1/2AC=1/2A1C1ï¼å³DA1=DC1
æå¾MD//AA1//BB1ï¼BB1DMæ¯ç©å½¢ï¼å¾BM//B1D
åç±äºB1Då¨é¢B1CPå
ï¼æ以BM//é¢B1CP
2ï¼å¨é¢ACC1A1ä¸è¿Aä½AEâ¥CPå足为E
ç±A1B1=B1C1ï¼DA1=DC1ï¼æå¾B1Dâ¥A1C1ï¼åç±é¢A1B1C1â¥é¢ACC1A1ï¼AEå¨é¢ACC1A1ä¸ï¼å¾B1Dâ¥AEã
åç±AEâ¥CPï¼æ
AEâ¥é¢B1CPãè¿æ¥B1Eï¼â AB1Eå³AB1ä¸é¢B1CPææçè§ï¼ä»¥ä¸æ±cosâ AB1E
ç±AB=BC=AA1=2ï¼å¾AB1=2â2
ç±â ABC=120°ï¼æå¾AC=2â3ï¼C1D=â3ï¼CD=â7
æå¾â³ACEâ½â³CDC1ï¼AE/AC=CC1/CDï¼å¾AE=4â21/7ï¼sinâ AB1E=AE/AB1=â42/7
cosâ AB1E=â7/7
温馨提示:答案为网友推荐,仅供参考