A sector of a circle of radius r cm has an area of A cm2. Express the perimeter of the sector in terms of r and A.
Solution
To find the perimeter of the sector, we need to express it in terms of the radius \(r\) and the area \(A\).
The area of a sector is given by \(A = \frac{1}{2} r^2 \theta\), where \(\theta\) is the angle in radians.
Rearranging for \(\theta\), we have:
\(\theta = \frac{2A}{r^2}\)
The perimeter \(P\) of the sector is the sum of the two radii and the arc length:
\(P = r + r + r\theta\)
Substituting \(\theta\) gives:
\(P = 2r + r \left( \frac{2A}{r^2} \right)\)
Simplifying, we get:
\(P = 2r + \frac{2A}{r}\)
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