Answer:
Let the radius of the circle be r cm and the arc Ab of length 5π cm subtends abgle θ at the centre O of the circle. Then ,
Arc AB=5 π cm and Area of sector OAB=20 πcm
2
⇒
360
θ
×2πr=5πand
360
θ
×πr
2
=20π
⇒
360
θ
×2πr
360
θ
×πr
2
=
5π
20π
⇒
2
r
=4
⇒ r=8cm
We have Area =
2
1
lr⇒20π=
2
1
×5π×r⇒r=8cm
solution
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