F.2 Maths

👨🏻‍🏫 學術台數學

Sze Man

2011-03-08 9:53 pm

The ratio of areas of a sector and the whole circle is 5:9. Find the angle at th-e centre of the sector.

回答 (2)

myisland8132

2011-03-08 10:01 pm

✔ 最佳答案

We have (1/2)r^2θ : πr^2 = 5 : 9

(1/2)θ : π = 5 : 9

θ : 2π = 5 : 9

9θ = 10π

θ = 10π/9 (radians) or 200 degrees

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Spencer

2011-03-09 8:26 am

簡答如下：

１）全個圓共：３６０度

２）全個圓的度數共分９份

３）扇形面積佔其中５份

４）每份度數＝３６０／９＝４０度

５）扇形面積佔其中５份，即：４０度x５份；即＝２００度

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