JAMB - Mathematics (1986 - No. 33)
An arc of a circle of radius 6cm is 8cm long. Find the area of the sector
5\(\frac{1}{3}\)cm2
24cm2
36cm2
84cm2
Explanation
Radius of the circle r = 6cm, Length of the arc = 8cm
Area of sector = \(\frac{\theta}{360}\) x \(\pi\)r2........(i)
Length of arc = \(\frac{\theta}{360}\) x 2\(\pi\)r........(ii)
from eqn. (ii) \(\theta\) = \(\frac{240}{\pi}\), subt. for \(\theta\) in eqn (i)
Area x \(\frac{240}{1}\) x \(\frac{1}{360}\) x \(\frac{\pi 6}{1}\)
= 24cm\(^2\)
Area of sector = \(\frac{\theta}{360}\) x \(\pi\)r2........(i)
Length of arc = \(\frac{\theta}{360}\) x 2\(\pi\)r........(ii)
from eqn. (ii) \(\theta\) = \(\frac{240}{\pi}\), subt. for \(\theta\) in eqn (i)
Area x \(\frac{240}{1}\) x \(\frac{1}{360}\) x \(\frac{\pi 6}{1}\)
= 24cm\(^2\)
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