Harriot, Thomas, Mss. 6785

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[Commentary:
On this page, Harriot works a problem from De regula aliza liber (Cardano , Chapter 41, pages 82–83. Cardano states the problem as follows:
De difficillimo problemate quod facillimum uidetur. CAP. XLI.
Nihil est admirabilius quam cum sub facili quaestione latet difficillimus scrupulus, huiusmodi est hic: quadratum ab cum latere bc est 10, & quadratum bc cum latere bd est 8, quaeritur quantum fit unum horum seu latus seu quadratum: Quia ergo abc est 10, & ab 1 quad. erit bc 10 m: 1 quad. igitur bc 100 m: 20 quad. p: 1 pos. p: 1 quad. quad. & hoc est aequale 8, quare 1 quad. quad. p: 92, aequatur 20 quad. m: 1 pos. adde 19 quad. utrinque fient 1 quad. quad. p: 19, quadrat. p: 92, aequalia 39. quad, m: 1 pos. detrahe 114, erunt 1 quad. quad. p: 19 quad. p: 9014 aequalia 39 quad. m: 1 pos. m: 114, inde adde 2 pos. p: 1 quad. utrinque ut in Arte magna, & videbis difficillimam quaestionem.

Chapter 41. On a very difficult question that seems easy.
Nothing is more remarkable than when under an easy question there lies a very hard stone, of which kind is this: the square of ab with the side bc is 10, and the square of bc with the side bd is 8; it is required to find one of those sides or squares. Therefore because abc is 10, and ab is one square, bc will be 10 minus a square. Therefore the square of bc is 100 minus 20 squares plus 1 square-square. Therefore bcd will be 100 minus 20 squares plus 1 unknown plus 1 square-square, and this is equal to 8, whence 1 square-square plus 92 equals 20 squares minus 1 unknown. Add 19 squares to each side, making 1 square-square plus 19 squares plus 92 equal to 39 squares minus 1 unknown. Subtract 114, to give 1 square-square plus 19 squares plus 9014 equal to 39 squares minus 1 unknown minus 114, whence add 2 unknowns plus one square to each side as in the Ars magna, and you will see this very difficult question.

Harriot lets the side of bc be a and then works through these instructions precisely. ]
Cardan. de Aliza. pa.
[Translation: Cardano, De regula aliza liber, page 83

[Translation: ]

Quæritur df vel fg
[Translation: Sought, df and fg.

[Translation: Another ]
Et per

[Translation: And by ]

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