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å¹³è¡å边形 (ABCD) ä¸ï¼(\angle BAC = 90^\circ)ï¼(\angle B = 45^\circ)ï¼ç¹ (P)ã(Q) åå«æ¯çº¿æ®µ (AD)ã(CB) ä¸çå¨ç¹ï¼ç¹ (E) å¨çº¿æ®µ (CQ) ä¸ï¼ä¸ (CE = 2AP)ï¼(QE = 2)ï¼è®¾ (AP) 为 (x)ã
(1) å½ç¹ (Q) è¿å¨å° (BC) ä¸ç¹æ¶ï¼æ°å¥½ (PE \perp BC)ï¼æ± (BC) çé¿åº¦ã
1. 设 (Q) 为 (BC) ä¸ç¹ï¼å (BQ = QC = \frac{BC}{2})ã
2. ç±äº (Q) 为ä¸ç¹ï¼æ以 (QE = 2)ï¼å³ (E) è·ç¦» (Q) 2åä½ã
3. å 为 (P) ç¹å¨ (AD) ä¸ï¼ä¸ (AD) ä¸ (BC) å¹³è¡ï¼æ以 (PE \perp BC) å³ (PE) ä¸ (AD) åç´ã
æ ¹æ®ä»¥ä¸ä¿¡æ¯ï¼å¯ä»¥ååºå ä½å
³ç³»ï¼å¹¶å©ç¨å¾è¡å®çæå
¶ä»å ä½æ¹æ³è§£é¢ã
(2) è¥ (BC = 12)ï¼æ¯å¦åå¨ (x)ï¼ä½¿å¾å边形 (ABQP) 为平è¡å边形ï¼è¥åå¨ï¼æ±åº (x) çå¼ï¼è¥ä¸åå¨ï¼è¯·è¯´æçç±ã
1. (BC = 12)ï¼å (BQ = QC = 6)ã
2. å¹³è¡å边形ç对边ç¸çä¸å¹³è¡ï¼èè (AP) å (BQ) çå
³ç³»ã
3. 计ç®å¹¶éªè¯ (x) çå¯è½å¼ã
(3) è¿æ¥ (PC)ï¼å½ç¹ (P) å¨è¿å¨æ¶ï¼(\frac{1}{2} AP + PC) ææå°å¼ä¸º (3 + 2\sqrt{3})ï¼æ±æ¤æ¶ (CQ) çé¿ã
1. (PC) é¿åº¦è®¡ç®æ¶åå°ä¸è§å½¢ (PCE) åç¹ (P) è¿å¨çä½ç½®ã
2. æ¾å° (AP) å (PC) çæä¼è§£ã
详ç»è§£ç
(1) 解ç
ç¹ (Q) æ¯ (BC) çä¸ç¹ï¼å设 (BC = y)ï¼å (BQ = QC = \frac{y}{2})ã
ç±äº (Q) å° (E) çè·ç¦»æ¯ 2ï¼å³ (QE = 2)ï¼ä¸ (CE = 2AP = 2x)ã
ä»å ä½å
³ç³»åºåï¼(PE \perp BC)ï¼å æ¤ (E) ä¸ (P) ä¹é´åå¨å¾è¡å
³ç³»ã
ç»å (AD)ã(BC) ä¹é´çå
³ç³»ï¼æ±åº (y) çå
·ä½å¼ã
(2) 解ç
设 (BC = 12)ï¼(BQ = QC = 6)ã
æ ¹æ®å¹³è¡å边形æ§è´¨ï¼éªè¯ (ABQP) å边形æ¯å¦ä¸ºå¹³è¡å边形ã
设 (x) 为åéï¼è§£åºæ¹ç¨ï¼æ¾åºæ»¡è¶³æ¡ä»¶ç (x) å¼ã
(3) 解ç
\frac{1}{2} AP + PC = 3 + 2\sqrt{3}
设 (AP = x)ï¼å (PC) å¯è¡¨ç¤ºä¸ºå½æ°å½¢å¼ï¼æ ¹æ®æå°å¼æ±è§£ï¼æ¾å°å
·ä½ CQ çé¿åº¦ã
å
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³ç³»ã代æ°æ¹ç¨åå¹³è¡å边形æ§è´¨ï¼éæ¥æ±è§£åå°é¢ï¼ç¡®ä¿è§£çåç¡®æ§ã
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