(1)由已知M(c, ), ∵kOM=kAB, ∴=, ∴b=c,e==
(2)设GF1=m,GF2=n, =∠F1GF2, cos==
=-1≥-1=0
当且仅当m=n时,(cos)min=0, ∴∈(0, ] (9分)
y=- (x-c)
(3) b2x2+a2y2=a2b2 5y2-2cy-2c2=0
a=c, b=c
|y1-y2|==c
S△PF1Q=|F1F2||y1-y2|=×2c×c=20
∴c2=b2=25, a2=50, ∴椭圆的方程为:+=1 (14分)
(1)由已知M(c, ), ∵kOM=kAB, ∴=, ∴b=c,e==
(2)设GF1=m,GF2=n, =∠F1GF2, cos==
=-1≥-1=0
当且仅当m=n时,(cos)min=0, ∴∈(0, ] (9分)
y=- (x-c)
(3) b2x2+a2y2=a2b2 5y2-2cy-2c2=0
a=c, b=c
|y1-y2|==c
S△PF1Q=|F1F2||y1-y2|=×2c×c=20
∴c2=b2=25, a2=50, ∴椭圆的方程为:+=1 (14分)