x1x22y1y22
1
A2B2

x1

x2
2

4x1x2
4m
A2B2A2mB2
C2
可得EFA2mB2

令A2mB2
则得到CGYEH定理
x1

x2

2ACm
mC2B2

x1x2

m
C2
2A2B2
EF
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