ç±y=-3x/4+6å¾A(8,0),B(0,6)ï¼AB=12ï¼OQ=tï¼AQ=8-tï¼AP=2tï¼0<=t<=8
ï¼1ï¼å½PQâ¥BOæ¶ï¼æ¤æ¶ä¸ºåå§ç¶æï¼t=0ï¼
å½PQâ¥BAæ¶ï¼ç±â³APQâ½â³AOBå¾AQ/AP=AB/AQï¼t=16/7ï¼
å½PQâ¥OAæ¶ï¼ç±PQ//OBå¾AQ/AP=AO/ABï¼t=40/13
ï¼2ï¼ç±ä½å¼¦å®çå¾PQ^2=AQ^2+AP^2-2AQ*APcosâ A=(8-t)^2+4t^2+16(t-8)t/5=(41t^2-208t)/5+64
对称轴t=104/41ï¼æ
å½0=<t<=8æ¶ï¼PQå
ååå¢ã
ï¼3ï¼Sâ³APQ=1/2*AP*AQsinâ A=3/5*(8-t)t=3/5(-t^2+8t)
å½t=4æ¶ï¼Sâ³APQææ大å¼ã
ï¼4ï¼å½På¨ABå
é¨ï¼å³0<=2t<=10ï¼0<=t<=5æ¶ï¼y=Sâ³AOB-Sâ³APQ=3/5(t^2-8t)+24
å½På¨ABå¤é¨ï¼å³5<=t<=8æ¶ï¼è®¾PQä¸OB交äºC
ç±Påå«åyè½´ãxè½´åå线æ¥æ±å¾Pç横纵座æ ï¼å AP=2tï¼æå¾P(8-8t/5,6t/5)
ç±Q(t,0),P(8-8t/5,6t/5)å¾ç´çº¿PQï¼y=6t(x-t)/(40-13t)
代å
¥x=0ï¼å¾y=6t^2/(13t-40),å³C(0,6t^2/(13t-40)),OC=6t^2/(13t-40)
y=Sâ³OQC=1/2*OQ*OC=3t^3/(13t-40)
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