/sci/ - Science & Math

Anonymous Tue Aug 13 16:40:02 2019 No.10885393 [View]
File: 12 KB, 768x564, cos(x+y).png [View same] [iqdb] [saucenao] [google]

>>10885332
Well you have a formula for cos(x-y) (which is actually cos(x)cos(y) _+_ sin(x)sin(y)), from there you deduce a formula for cos(x+y), substract the two and Bob's your uncle.
Now the real interesting question is how you prove that formula for cos(x+y).
You can find a nice geometric proof of this starting from pic related and using some projections and the pythagorean theorem

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/sci/ - Science & Math

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