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A circular cross-section.
Circular when looking up at it
triangle
a square
For a right cone, it is a hyperbola which becomes and isosceles triangle when the section passes through the apex.
The cross section will be a triangle with base 2 feet and a vertical height of 9 feet.
No. Some of the classic curves studied by mathematicians: ellipses, hyperbola are cross sections of a cone taken at an angle.
Circle
The answer depends on the angle at which the axis of the cone intersects the cross-sections.
If it a right cone then it is a circle, otherwise an ellipse.
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Circle
A circular cross-section.
Circular when looking up at it
cone
triangle