because

∠BDC=∠CEB

therefore

∠CDA=∠BEA

∠A

=∠A

AD=AE

△ADC congruence△△ AEB

AB=AC

BD=CE

6. Because: AB//A'E'

Alternating current//alternating current

therefore

∠C=∠B'C'A '

∠B'=∠CBA

because

BB'=CC '

therefore

BC = BC

△ABC congruence△ a' b' c'

AC=A'C '

7. Because △ ABC△ a' b' c'

therefore

AB=

A b

∠B=∠B '

And because of AD. A'D' is the height of △ABC and △A'B'C' respectively.

therefore

∠ADB=∠A'D'B '

△ABD?△A ' b ' d '

therefore

AD=A'D '

8. The following is omitted

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principle

Same thing