In the derivation of the formula for the volume of a cone, the volume of the cone is calculated to be [tex]$\frac{\pi}{4}$[/tex] times the volume of the pyramid that it fits inside.

Which statement best describes where the [tex]$\frac{\pi}{4}$[/tex] comes from in the formula derivation?

A. It is the ratio of the area of the square to the area of the circle from a cross section.
B. It is the ratio of the area of the circle to the area of the square from a cross section.
C. It is the difference of the area of the square and the area of the circle from a cross section.
D. It is the sum of the area of the square and the area of the circle from a cross section.



Answer :

To determine where the [tex]\(\frac{\pi}{4}\)[/tex] factor comes from in the derivation of the volume of a cone compared to the volume of the pyramid that it fits inside, we need to consider the areas of the cross-sections involved.

1. If you take a cross-section of the cone, you will obtain a circle. Let's denote the radius of this circle as [tex]\(r\)[/tex]. The area of the circle, [tex]\(A_{\text{circle}}\)[/tex], is given by:
[tex]\[ A_{\text{circle}} = \pi r^2 \][/tex]

2. If you take a cross-section of the square pyramid in which the cone fits, you will get a square. Suppose the side length of this square is [tex]\(2r\)[/tex] (i.e., a square that can circumscribe the circle). The area of the square, [tex]\(A_{\text{square}}\)[/tex], is:
[tex]\[ A_{\text{square}} = (2r)^2 = 4r^2 \][/tex]

3. The ratio of the area of the circle to the area of the square is:
[tex]\[ \frac{A_{\text{circle}}}{A_{\text{square}}} = \frac{\pi r^2}{4r^2} = \frac{\pi}{4} \][/tex]

Therefore, the [tex]\(\frac{\pi}{4}\)[/tex] comes from the ratio of the area of the circle to the area of the square from a cross-section. Thus, the best statement that describes the origin of the [tex]\(\frac{\pi}{4}\)[/tex] factor in the formula derivation is:

It is the ratio of the area of the circle to the area of the square from a cross section.