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Congruent triangles is a big problem! ! Advanced mathematics
( 1)

Let AD be the center line of BC side in △ABC.

Get BD=CD

Because CE‖AB

It is concluded that ∠ABD=∠DCE, ∠BAD=∠CED (the lines are parallel and the internal dislocation angles are equal).

BD=CD,∠ABD=∠DCE,∠BAD=∠CED

Get △ Abd△ CDE.

So AB=CE

(2)

AD=DE is obtained from △ Abd △ CDE.

So 2AD=AD+DE=AE.

△AC+CE > in△ACE; AE (the sum of two sides of a triangle is greater than the third side)

So AC+CE >;; 2AD

And because AB=CE (proved)

So 2ad