MATH QUESTIONS [CIRCLE]－新聞雲

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MATH QUESTIONS [CIRCLE]

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8. 圖片參考：http://imgcld.yimg.com/8/n/HA00610265/o/701009170093113873371730.jpg O is the centre.AOEC is astraight line. If angle BCE = 70, find angle EDC.15.圖片參考：http://imgcld.yimg.com/8/n/HA00610265/o/701009170093113873371741.jpg O is the centre, A,B, C , D and E are points lying on the circle. If... 顯示更多 8. 圖片參考：http://imgcld.yimg.com/8/n/HA00610265/o/701009170093113873371730.jpg O is the centre.AOEC is astraight line. If angle BCE = 70, find angle EDC. 15. 圖片參考：http://imgcld.yimg.com/8/n/HA00610265/o/701009170093113873371741.jpg O is the centre, A,B, C , D and E are points lying on the circle. If angle EOC = 110 and Angle ABC = 130, find angle ADE 17. 圖片參考：http://imgcld.yimg.com/8/n/HA00610265/o/701009170093113873371742.jpg AB is the diameter and O is the centre. BC and OD intersects at E and AB //CD. if angle ODC = 56, find angle OEB.

最佳解答:

8: Let AB. ∠ABC=90度 (angle in semi circle) ∠BAC=180-70-90=20度 so ∠EDC=20度 (同弓形內的圓周角) 15.let DC ∠ADC=180-30=50 (圓內接四邊形對角) ∠EOC=360-110=250 ∠EDC=250/2=125 (圓心角兩倍於圓周角) so ∠ADE=125-50=75度 17.sinceAB//CD , ∠DOB=56 ∠BCD= 56/2=28 (圓心角兩倍於圓周角) ∠CED=180-28-56=96 so , ∠OEB=96度 -------------------------------------------------------------- 唔知岩唔岩~~