Disc Cones
Proof for volume of a cone using solids of revolution?
I DON'T GET IT 
I know that I'm supposed to be taking little disks of something.
so if I have a triangle of height h and base r, and I want to revolve it around the y-axis...
then i want to be adding pi*r² values of very small circles up the y-axis right?
So it would be like pi*r² where r = ???????? How can I get something for r here??
PLEASE HELP! DESPERATE
Thank you!
The key is, you're not adding "very small circles" up the y-axis, you're adding very small approximate-cylinders up the y-axis (what you call disks), where the radius of the cylinder is approximately r (which will vary with the distance from the base) and the height of the cylinder is delta y. As you increase the number of cylinders, the radius of each approaches r, and the height of each gets smaller and smaller, called dy. So, if there is a known relationship between the radius r and the distance along the y-axis (which, of course there is: r = (R / h) * y , for an upside down cone with tip at the x-axis and base at height h above it), the sum of the volumes approaches the integral of pi*r2 *dy over the interval y=0 to y=h. Substituting (R/h)y for r, and solving the integral, gives 1/3 * pi * r2 * h.
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Set of 25 World Sport Disc Cones (6 Colors to Choose From) |
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Used by top coaches around the world. A highly versitle training aid for coaches of any field sport (Soccer, Football, La Crosse, Field Hockey etc). These cones are used to mark boundaries, set up a slalom run forcing change of speed and direction and can be used to create goals for small sided games. Manufactured with safety in mind. Low profile dics prevent injury when fallen upon. |
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World Sport Disc Cone Sets (50 or 100 Multi Color / 50 or 100 Half Orange Half Yellow) |
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Used by top coaches around the world. A highly versitle training aid for coaches of any field sport (Soccer, Football, La Crosse, Field Hockey etc). These cones are used to mark boundaries, set up a slalom run forcing change of speed and direction and can be used to create goals for small sided games. Manufactured with safety in mind. Low profile dics prevent injury when fallen upon. |
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Disc Cone Carrier Sale Price: $6.95 |
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Disc cone carrier holds up to 200 cones. |
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Disc Cones - Set of 50 Orange With Carrier Sale Price: $20.00 |
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No coach should be without this set of 50 marking cones, an essential at no matter what level you coach. At this price no coach can do without. Bright orange, they can be used for many activities and games. Use for drills, sideline/boundary markers, obstacles, targets. 2" high. Stackable for easy storage. Set of 50 with holder. |
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Set of 20 Disc Cones Bright Orange Sale Price: $11.99 |
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No coach should be without marking cones, an essential at no matter what level you coach. At this price no coach can do without. Bright orange, they can be used for many activities and games. Use for drills, sideline/boundary markers, obstacles, targets. 2" high, set of 20. Stackable for easy storage. |
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Kwik Goal Disc Cone (Pack of 25) |
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Small disc training cones - 25 per pack - Blue |
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Kwik Goal Jumbo Disc Cones |
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Small disc training cones with cradle - 25 per pack - Yellow |
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Disc Cones - Set of 50 Multi-Color Sale Price: $24.99 |
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No coach should be without this set of 50 marking cones, an essential at no matter what level you coach. At this price no coach can do without. Bright, colorful, can be used for many activities and games. Use for drills, sideline/boundary markers, obstacles, targets. 2" high. Stackable for easy storage. Set of 50. Colors: red, luminous green, white, yellow, blue. |
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Set of 10 Orange Disc Cones Sale Price: $4.00 |
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No coach should be without marking cones, an essential at no matter what level you coach. At this price no coach can do without. Bright orange, they can be used for many activities and games. Use for drills, sideline/boundary markers, obstacles, targets. 2" high. Stackable for easy storage. |
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Set of 30 Disc Cones Bright Orange Sale Price: $15.99 |
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No coach should be without marking cones, an essential at no matter what level you coach. At this price no coach can do without. Bright orange, they can be used for many activities and games. Use for drills, sideline/boundary markers, obstacles, targets. 2" high, set of 30. Stackable for easy storage. |
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