The second problem of mathematics in the second day of junior high school

Solution: DC, for the following reasons:

In triangle ABD and triangle ADF:

AD=AD

& ltDBA =< automatic direction finder

& ltBAD =< flavin adenine dinucleotide

So triangle ABD and triangle ADF are congruent.

So BD=DF

In triangle EDB and triangle CDF:

BD=DF

& ltDBA =< automatic direction finder

BE=CF

So the triangle EDB is equal to the triangle CDF.

So DC = Germany

Please ask questions and praise if you don't understand.

Of course, Pythagorean theorem can also be used.

According to the meaning of the question

∠ABC = ∠DFC = 90

And because BE = CF

According to Pythagorean theorem

ED^2=CD^2

So DC = Germany

Solve it manually and ask FVF for praise.