1/2aT1^2=x
aT1T2+1/2aT2^2=x
所以1/2aT1^2=aT1T2+1/2aT2^2
T1^2=2T1T2+T2^2
T1^2/T2^2=2T1/T2+1
T1/T2=1+根号2:1