Show that the height of the cone of maximum volume that can be inscribed in a sphere of radius 12 cm is 16 cm.

Let a cone of radius r cm and height h cm is inscribed in a sphere of radius 12 cm.

In right triangle AOB,

(12)2 =  (h – 12)2 + r2

r2 =24h – h2

Now, V = (1/3)πr2h

V =  (1/3)π(24h – h2)h  (Substituting the value of r2)

V = (1/3) π(24h2 – h3)

dV/dh = (1/3) π (48h – 3h2)

For maximum volume: dV/dh = 0

Therefore, we get

(1/3) π (48h – 3h2) = 0

48h – 3h2 = 0

h = 16.

Also, d2V/dh2 = 1/3 π (48 – 6h)

(d2V/dh2 )h = 16 =  1/3 π (48 – 96) < 0.

Therefore, for h = 16, volume is maximum.

Hence, height of the cone  of maximum volume, which can be inscribed in a sphere of radius 12 cm is 16 cm.

 

 

 

 

 

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