Question

如图,AB平行于EF,角C=90度,试探究：角B,角CDE,角E之间的数量关系,并说明理由

Answer 1

∠CDE=90°+∠DEF-∠ABC
过点C、D分别作AB的平行线CM、DN
AB//EF
AB//EF‖CM‖DN
∠ABC=∠BCM
∠MCD=∠CDN
∠NDE=∠DEF
∠CDE=∠CDN+∠NDE
=∠MCD+∠DEF
=∠BCD-∠BCM+∠DEF
=90°-∠ABC+∠DEF
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