maths-circle
2011-02-10 3:53 am
圖片參考：http://img135.imageshack.us/img135/118/17397953.jpg
In the figure, A,B,C,D,and E are points on the circumference. ∠DBE=70°, ∠BCD=x and ∠BAE=y, find x+y
回答 (2)
2011-02-10 4:03 am
✔ 最佳答案
角BDC=180-y(opp.angle,cyclic quad)角BED=180-x(opp.angle,cyclic quad)
In triangle BED,
角B+角E+角D=180(angle sum of triangle)
70+(180-x)+(180-y)=180
x+y=250
2011-02-10 4:10 am
Join CE ,
y + ∠ BCE = 180° (opp. ∠s, cyclic quad.)
∠ ECD = ∠ EBD = 70° (∠s in the same segment)
x + y = 180 + 70 = 250
y + ∠ BCE = 180° (opp. ∠s, cyclic quad.)
∠ ECD = ∠ EBD = 70° (∠s in the same segment)
x + y = 180 + 70 = 250
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110209000051KK01440