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ææä¸è§å½¢ç两边çå两ä½OA=(x1,y1), OB=(x2,y2)
é£ä¹ÎOABçé¢ç§¯ä¸ºcx1y2-x2y1|
设A(â2cost1, sint1)ï¼B(â2cost2, sint2)
æ以OA=(â2cost1, sint1)ï¼OB=(â2cost2, sint2)
æ以SÎOAB=(1/2)|â2sint2cost1-â2cost2sint1|=(â2/2)|sin(t2-t1)|
å¾ææ¾ï¼å½t2-t1=Ï/2æ¶ï¼SÎOABåå°æ大å¼ã
t2=t1+Ï/2ï¼é£ä¹A(â2cost1, sint1)ï¼B(-â2sint1, cost1)
为äºç®ä¾¿è®¡ç®ï¼ç¨tæ¥ä»£æ¿t1ï¼æ以A(â2cost, sint)ï¼B(-â2sint, cost)
å 为M(0,2)åAï¼Bå
±çº¿ï¼MA=(â2cost, sint-2)ï¼MB=(-â2sint, cost-2)
æ以-sint/cost=(cost-2)/(sint-2)
å¾å°sint+cost=1/2
ä¸(sint)^2+(cost)^2=1
å¾å°sintcost=[(sint+cost)^2-1]/2= -3/8
æ以(sint-cost)^2=1-2sintcost=7/4
sint-cost=屉7/2
é£ä¹kAB=(sint-cost)/â2(sint+cost)=±â14/2
æ以å¾å°ç´çº¿æ¹ç¨ä¸ºâ14x-2y+4=0æè
â14x+2y-4=0
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