A cylinder of cheese is to be removed from a spherical piece of cheese with a radius of 8 cm what's the maximum volume of the cylinder piece of cheese



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Posted on (Answer #1)

Draw a circle on the plane with it's centre at the origin and a rectangle in it representing a 2D slice of the cylinder.
The radius of the circle, R = 8 cm points to one corner of the rectangle.
The radius of the cylinder (i.e. half the width of rectangle) is `r = Rcostheta`
the height of the cylinder is `h = 2Rsintheta`
Volume of the cylinder `V = pir^2h`

Putting the values of r and h we get:
`V = pi(Rcostheta)^2(2Rsintheta) = 2piR^3cos^2thetasintheta`
For extremum (maximum or minimum) value of V,
`(dV)/(d theta)=0`
`rArr 2piR^3(cos^2theta*costheta + sintheta*2costheta*(-sintheta)) = 0`

`rArr 2piR^3(cos^3theta - 2sin^2thetacostheta)=0`
`rArr 2piR^3costheta(cos^2theta - 2sin^2theta)=0`

Therefore, Either, `costheta=0` , That corresponds to V=0 (minimum value)

Or, `cos^2theta-2sin^2theta=0`

`rArr cos^2theta = 2sin^2theta`
`rArr tan^2theta = 1/2`

Or,`tantheta = 1/sqrt2`
Forming a right triangle with this tan value yields

`sintheta = 1/sqrt3 and costheta = sqrt2sintheta`
Therefore, the maximum volume of the cylindrical piece of cheese





`=1238.2 cm^3`

So, the maximum volume of the cylindrical piece of cheese that can be cut out from the spherical cheese ball is 1238.2 cm^3.



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