例6求步骤

问题描述:

谢谢老师
4个回答 分类:数学 2014-09-19

问题解答:

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解题思路: 结合三角形相似进行求解
解题过程:
解:
∵AB=AC,∠BAC=120°,∴∠B=∠C=30°,
∴∠CFD=180°-∠C-∠FDC=180°-30°-∠FDC=150°-∠FDC
又∵∠BDE=180°-∠EDF-∠FDC=180°-30°-∠FDC=150°-∠FDC
∴∠BDE=∠CFD,
又∠B=∠C,
∴△BDE∽△CFD,
∴BD/CF=ED/DF
∴ED/BD=DF/CF,
∵BD=DC,∴ED/CD=DF/CF,
又∠EDF=∠C=30°
∴△EDF∽△DCF,
∴∠EFD=∠DFC
∵∠DFC=180°-∠C-∠FDC=180°-30°-x=150°-x°
∴y=150-x
 
 
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补充回答:

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Three, July half of the ancient custom of ancestor worship, its birth can be traced back to the ancient times of ancestral worship and related time offerings. Originally is the folk festival of ancestor worship, rather than "ghost festival", July half culture core is filial piety, generally will not sacrifice to the ancestors of the festival called "ghost festival (" ghost festival "is later said, is supposed to be from the Taoist Yuan Purdue open the thought of the gate of death evolved).
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