F.2 MATHS (10點~~~)
2008-01-21 5:33 am
if the length of an arc is 5cm and the redius of the circle is 1.4cm,find the angle of the arc subtending at the cente.(give your answer correct to th nearest degee.)
回答 (2)
2008-01-21 5:59 am
✔ 最佳答案
θ = angle of the arc substending at the centreS = arc length
r = radius of the circle
S = rθ
5 = 1.4θ
θ = 3.57 rad
θ = 205°
2008-01-21 7:46 am
Let θ be the angle of the arc subtending at the cente
2πr x (θ/360)=arc length
Now r = 1.4, arc length=5
So
2 x 1.4 x π x (θ/360)=5
2.8π x (θ/360)=5
(θ/360)=5/(2.8π)
θ=(360)(5/(2.8π))
θ=204.627784°
So θ=205°(correct to the nearest degee)
So the angle of the arc subtending at the cente is 205°
2πr x (θ/360)=arc length
Now r = 1.4, arc length=5
So
2 x 1.4 x π x (θ/360)=5
2.8π x (θ/360)=5
(θ/360)=5/(2.8π)
θ=(360)(5/(2.8π))
θ=204.627784°
So θ=205°(correct to the nearest degee)
So the angle of the arc subtending at the cente is 205°
參考: My maths knowledge
收錄日期: 2021-04-13 15:00:02
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