How did Cavalieri get his formula for the area underneath a parabola?

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    Area Formula Parabola
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SUMMARY

Cavalieri derived his formula for the area underneath a parabola using the sum of squares formula: $$\sum_{k=1}^m k^2 = \frac{m(m + 1)(2m + 1)}{6}$$. By substituting the sum of squares into his initial equation, he was able to achieve the desired result. This method highlights the significance of mathematical ratios and summation techniques in deriving geometric properties.

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I know he had this ratio:
1604325468203.png

But how did he get this:
1604325593307.png
?
 
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erocored said:
I know he had this ratio:
View attachment 272042
But how did he get this:
View attachment 272043 ?
The result uses a formula for the sum of squares.
$$\sum_{k=1}^m k^2 = \frac{m(m + 1)(2m + 1)}6$$
Replace ##1^2 + 2^2 + \dots + m^2## in your first equation by the above, and you will get the result shown in the second equation.
 
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