# Calculation of the volume of an ellipse cone

I am trying to work out a formula for the approximate calculation of the lung capacity of a racehorse.

I take three physical dimensions on the horse.

1) The measurement of the girth (which is the perimeter of an ellipse) around the horse.
2) the measurement from the top of the withers which coincides with the top of the girth to the point of the hip (B to C)
3) the measurement from the bottom of the girth to the point of the hip (A to C)

Some real data

Girth Circumference (perimeter of Ellipse) - 172 cm
Distance B to C - 65 cm
Distance A to C - 85 cm

The minor axis and major axis ratio’s are approximations that I have made after measuring a few 100 horses.

Major Axis is B to C divided by 2.25 (in this case 76.44)
Minor Axis is A to C divided by 5.75 (in this case 29.91)

I tried using the Heron formula to calculate the height of the triangle and then calculated the Area of the Ellipse ((Pi*Major*Minor)/4) and then calculated the Volume ((base*height)/3)

The volume figures that I am coming up with don't correspond to physical calculations of lung volume in the veterinary world. I am not expecting it to be perfectly accurate, just an approximation, but the figures I am getting are too far away from reality.

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I should have added that the cone is obviously not an equilateral cone/triangle.

Any help most appreciated.

Ray Vickson
Homework Helper
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I should have added that the cone is obviously not an equilateral cone/triangle.

Any help most appreciated.

Standard formula: ##V = \frac{1}{3} A h##, ##A=## area of base, ##h =## height. This is the volume formula for a pyramid, but the bottom need not be a rectangle and the thing can be tilted, as is yours. The reason is simple: the area ##a(x)## at a height ##x## from the apex is ##a(x) = A (x/h)^2## (because the lateral dimensions are proportional to ##x##, so the area is proportional to ##x^2##) Now integrate: ##V = \int_0^h a(x) \, dx.##

Standard formula: ##V = \frac{1}{3} A h##, ##A=## area of base, ##h =## height. This is the volume formula for a pyramid, but the bottom need not be a rectangle and the thing can be tilted, as is yours. The reason is simple: the area ##a(x)## at a height ##x## from the apex is ##a(x) = A (x/h)^2## (because the lateral dimensions are proportional to ##x##, so the area is proportional to ##x^2##) Now integrate: ##V = \int_0^h a(x) \, dx.##

Ray. Appreciate the feedback. Is there an easy way to write this in an Excel cell?

Ray Vickson