[ \frac{\text{Area of the sector}}{\text{Area of the circle}} = \frac{\text{Arc length of the sector}}{\text{Circumference of the circle}} ]
[ \text{Area of the sector} = \frac{\text{Arc length of the sector}}{\text{Circumference of the circle}} \times \text{Area of the circle} ]
[ = \frac{s}{2\pi l} \times \pi l^2 = \frac{s}{2} \times l = \frac{2\pi r}{2} \times l \quad (\because s = 2\pi r) ]
[ \text{Curved Surface Area of the cone} = \text{Area of the Sector} = \pi rl \text{ sq. units.} ]
[ \text{C.S.A. of a right circular cone} = \pi rl \text{ sq. units.} ] [[]]“
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