- #1

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sin(a - b) = sin(a)cos(b) - cos(a)sin(b)

cos(a + b) = cos(a)cos(b) - sin(a)sin(b)

cos(a - b) = cos(a)cos(b) + sin(a)sin(b)

Who first derived them? When, and how?

Thanks

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- #1

- 209

- 1

sin(a - b) = sin(a)cos(b) - cos(a)sin(b)

cos(a + b) = cos(a)cos(b) - sin(a)sin(b)

cos(a - b) = cos(a)cos(b) + sin(a)sin(b)

Who first derived them? When, and how?

Thanks

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- #2

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ImAnEngineer said:Who first derived them? When, and how?

Not how, but Howe … Julia Ward Howe, in 1861, derived them, and they became a Civil War marching song, to the tune now known as the Battle Hymn of the Republic.

- #3

- 209

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If it's a joke... sorry but I don't get it.tiny-tim said:Not how, but Howe … Julia Ward Howe, in 1861, derived them, and they became a Civil War marching song, to the tune now known as the Battle Hymn of the Republic.

- #4

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ImAnEngineer said:If it's a joke... sorry but I don't get it.

try singing it!

- #5

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tiny-tim said:

try singing it!

Struggling to get a nice melody... :P

Any serious comments?

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