Question

如图,在△abc中,∠b=∠c,ad平分∠bac,∠bad=40°,且∠ade=∠aed,求∠cde的度数.

Answer 1

∵AB=AC,∴△ABC是等腰△,

又∵AD平分∠BAC,∴AD⊥BC,

∴∠ADB=∠ADC=90°,

∴∠BAD=∠CAD=40°,

∴∠C=50°,

∵∠ADE=∠AED,

∴∠ADE=﹙180－40﹚／2=70°,

∴∠CDE=90°－70°=20°