In two congruent triangles, angle B= angle EDF.

In triangle DBC, angle CDB+ angle B+ angle 2= 180 degrees.

And angle 1+ angle EDF+ angle CDB= 180 degrees. So the angle 1= angle 2.

If DH is perpendicular to BC from the midpoint D, it can be proved that DH is parallel and equal to half of AC, then H is the midpoint of BC. It can be proved that the triangle CDH and BDH are congruent. So angle 2 = angle b

So the angle 1 = angle b, so DG is parallel and equal to half of BC, so G is the midpoint of communication. You can find Gc = 1/2ac = 4.

(2) If M coincides with C, it proves that AD = CD = BD = 5, then let NH be perpendicular to CD in H, prove that H is the midpoint of CD, and the angle CNH= angle F, and prove that the two triangles CNH are similar to the angle FDE. Therefore, CN/CH=FD/DE and cn = 25/6 are the minimum values of X. Similarly, X is at most 6.