C2:(y/b)^2-(x/a)^2= 1

E 1= under the radical sign (1+b 2/a 2)

E2= under the root sign (1+A 2/B 2)

e 1+e2=t

t^2=2+a^2/b^2+b^2/a^2+

2t

t^2-2t-(b^2/a^2+a^2/b^2+2)=0

Then find the root.

You can set b 2/a 2+a 2/b 2 = v (greater than or equal to 2).

△=4+

4v

+8= 12+4v

Tmin = (under 2+radical sign (12+4V))/2 ((under 2-radical sign (12+4v))/2) truncation)

So when v takes 2, it is the minimum value.

That is tmin=3.