(2)∠AEC= 135？

(3) Because ∠B+∠D=90? ，∠A+∠C= 180？ ，∠AED=∠CEB=45？

So ∠A+∠D= 135? ，∠B+∠C= 135？

So, ∠A= 135? -∠D，∠B=90？ -∠D，∠C=45？ +∠D

According to Zheng Xuan's theorem, AE/sin∠D=AD/sin45? =6 and BE/sin(45? +∠D)=BC/sin45？ =√2

AB=AE+BE=6sin∠D+√2sin(∠D+sin45？ )=7sin∠D+cos∠D

According to the orthomorphism theorem, DE/sin( 135-∠D)=AD/sin45? =6, and CE/(sin90? -∠D)=BC/sin45？ =√2

CD=DE+CE=6sin( 135？ -∠D)+√2cos∠D=4√2，

Therefore, (3sin∠D)/4+cos∠D= 1, press sin? ∠D+cos？ ∠D= 1

Solve sin∠D=24/25 and cos∠D=7/25.

Because AB=7sin∠D+cos∠D=7.