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標題:
Maths(area and volume)
發問:
The figure shows a frustum ABCD of a right circular cone VBC.The radii of the upper base and the lower base are 2cm and3cm respectivel.The height of the frustum is 3cm. a)Find VP 圖片參考：http://imgcld.yimg.com/8/n/HA00772322/o/701101300127713873375650.jpg 更新: 點解5係 VP VD ----- = ------ ，VP：PQ，VD：CD ？ PQ CD
最佳解答:
Consider triangle VPD and triangle VQC They are similar triangles because they have same internal angles. (90o, angle C and angle PVD) Using ratio VP VQ ----- = ------ PD QC Let VP = x cm and VQ = VP + PQ x x + 3 ----- = ------ 2 3 3x = 2(x + 3) 3x = 2x + 6 3x - 2x = 6 x = 6 VP = 6 cm 2011-02-03 21:47:33 補充： To Amy: PQ // QC angle VDP = angle VCQ (corresponding angles) tan angle VDP = tan angle VCQ (trig. function ) So VP/PD = VQ/QC Godfrey 2011-02-03 21:55:44 補充： Sorry, typo error in 意見: PD // QC (not PQ // QC) Alternatively, triangle VPD is similar to triangle VQC Using ratio, VP/PD = VQ/QC
其他解答:
Maths(area and volume)
發問:
The figure shows a frustum ABCD of a right circular cone VBC.The radii of the upper base and the lower base are 2cm and3cm respectivel.The height of the frustum is 3cm. a)Find VP 圖片參考：http://imgcld.yimg.com/8/n/HA00772322/o/701101300127713873375650.jpg 更新: 點解5係 VP VD ----- = ------ ，VP：PQ，VD：CD ？ PQ CD
最佳解答:
Consider triangle VPD and triangle VQC They are similar triangles because they have same internal angles. (90o, angle C and angle PVD) Using ratio VP VQ ----- = ------ PD QC Let VP = x cm and VQ = VP + PQ x x + 3 ----- = ------ 2 3 3x = 2(x + 3) 3x = 2x + 6 3x - 2x = 6 x = 6 VP = 6 cm 2011-02-03 21:47:33 補充： To Amy: PQ // QC angle VDP = angle VCQ (corresponding angles) tan angle VDP = tan angle VCQ (trig. function ) So VP/PD = VQ/QC Godfrey 2011-02-03 21:55:44 補充： Sorry, typo error in 意見: PD // QC (not PQ // QC) Alternatively, triangle VPD is similar to triangle VQC Using ratio, VP/PD = VQ/QC
其他解答:
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