营销资料
幼苗
共回答了11个问题采纳率:90.9% 举报
F(P/2,0) A(P/2+2R,0) C(P/2+R,0)圆方程:(x-P/2-R)^2+y^2=R^2y^2=2Px(x-P/2-R)^2+2Px=R^2化简 x^2+(P-2R)x+(P^2)/4+PR=0x1+x2=-P+2R(FM+FN)/R=(X1+P/2+X2+P/2)/R=2 设椭圆方程为x^2/a^2+y^2/b^2=1 F(-c,0) A(-c+2R,0) C(-c+R,0) a^2=b^2+c^2 e=c/a圆C方程: (x+c-R)^2+y^2=R^2与椭圆方程联立 得:(b^2/a^2)x^2-(x+c-R)^2=b^2-R^2化简得:(-c^2/a^2)x^2-2(c-R)x-a^2+2cR=0FM=c/a *(x1+a^2/c)FN=c/a *(x2+a^2/c)(FM+FN)/R=[c/a*(x1+x2)+2a]/R={c/a*[-2(c-R)/(-c^2/a^2)]+2a}/R=2a/c=2/e
1年前
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