# I tried and am lost, please show me how, thanks

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Posted by Kurt on October 07, 2002 at 20:44:52:

In Reply to: Re: Thanks; BUT how do I get an equation in order to maximize it??? posted by Subhotosh Khan on October 07, 2002 at 14:33:00:

: : : : A disk has a V cut to the centre and rolled and sealed into a cone.
: : : : The cutout V is also rolled into a cone and sealed.
: : : : What would the angle of the V be in order that the sum of the volumes of the two cones be a maximum?.

: : : : Thank you in advance.
: **************************************
: 1) Draw a picture of a circle - center at O

: 2) Draw an angle AOB - AB on the circumference of the circle. This is the piece you are cutting out.

: 3) Now for the smaller cone, The base is made out of circle whose circumference is AB (what is the length of AB if mAOB = T). From that you can get the area of the base(A_1). The height of the cone is R. So the volume of the small cone (V_1)=1/3*R*A_1

: 4) similarly find V_2 - the volume of Larger cone

: 5) V = V_1 + V_2 ... this will be function of 'T'(=mAOB)

: 6) differntiate and set it to zero to find maximum.

: If need more help - show your work

:
: : : Things you know and can calculate:

: : : The distance from the top of the cone to the bottom along the edge of
: : : the cone is the same for both cones and is equal to the radius of the
: : : original disk.

: : : You can find the circumference of both cones as a function of the
: : : angle of the V.

: : : From the circumference of the cone you can find the radius of the base
: : : and then the height of the cone.

: : : From the height and the radius you can find the volume of the cones.

: : :
: : : This is a simple problem with multiple steps. When doing a problem
: : : with multiple steps try and break things down into simple pieces. Ask
: : : yourself what can I calculate? Draw a good picture, start labeling
: : : things in terms of what you know, even if you don't think you will need
: : : it.

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