17.C1:x^+y^=4交x轴于A1(-2,0),A2(2,0),设直线l:x=m,它交C1于B1(m,√(4-m^)),B2(m,-√(4-m^)),A1B1:y=√(4-m^)/(m+2)*(x+2),①A2B2:y=-√(4-m^)/(m-2)(x-2).②①*②,y^=x^-4,∴x^/4-y^/4=1,为P的轨迹C2的方程。(2)设切点M(x1,y1),N(x2,y2),则切线MG:x1x+y1y=4,NG:x2x+y2y=4,设G(2sect,2tant),则MN:x*2sect+y*2tant=4,交x轴于E(2cost,0),交y轴于H(0,2cott),∴1/OE^-1/OH^=1... |