Is the curved surface area of cone RH ???? or is it
Rl ???
Consider a hollow cone of radius (R) and height (H)...to find the surface area of the hollow cone consider a small segment dy at a height y from the top and with a radius r as shown in fig,
now
area of small element dy = 2r.dy
integrating to get area of hollow cone
surface area =
r=Ry / H (by similarity of triangles)
now carrying out the integration
we get,
surface area of a hollow cone = RH = curved surface area
but we know that the curved durface area of a cone is rl ..... so how......
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