第41页

信息发布者：
B
$60°$
4
$24°$
A
$60°$
$30°$
6或12
解：$\because AC=CD=BD=BE，$$∠ A=50°，$
$\therefore ∠ A = ∠ CDA = 50°，$$∠ B = ∠ DCB，$$∠ EDB = ∠ DEB。$
$\because ∠ CDA$是$△ BDC$的外角，
$\therefore ∠ CDA = ∠ B + ∠ DCB，$
$\therefore ∠ B = 25°。$
$\because$ 在$△ BDE$中，$∠ B + ∠ EDB + ∠ DEB = 180°，$
$\therefore ∠ EDB = \frac{1}{2} × (180° - 25°) = 77.5°，$
$\therefore ∠ CDE = 180° - ∠ CDA - ∠ EDB = 180° - 50° -77.5° = 52.5°$
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