A semicircular lamina of radius 35cm is folded so that the two bounding radii are joined together to form a cone. Find the radius and the lateral surface area of the cone.
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Length of the arc AB = theta/360 *2*pie*r
In case of semicircle theta=180°
Length of the arc AB= 180/360*2*pie*r = pie*r,
Where r =35cm
Length of the arc AB= 35 pie cm
Also the circumference of the base of cone will be equal to thelength of the arc. i.e., 2*pie*r = 35pie
r= 35/2 = 17 .5cm
C.S.A of the cone= pie*r*l where l is the slant height which will be equal to the radius of the original semi circular sheet.
i.e., C.S.A = pie*17.5*35
C.S.A = 1925 cm^2
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