how to prove cos(x+y)=cosxcosy-sinxsiny?

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how to prove cos(x+y)=cosxcosy-sinxsiny?

and if possible how to prove sin(x+y)=sinxcosy+cosxsiny

I know how to prove that one, but I am having trouble proving cos(x+y) if you can could you insert diagrams, if not, can you direct me to a page with how to prove it?? THANK YOU SO MUCH!

2007-01-03 09:49:11 · 2 answers · asked by goesonyahooanswerswhenbored 3 in Science & Mathematics ➔ Mathematics

2 answers

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2007-01-03 10:06:17 · answer #1 · answered by epaphras_faith 4 · 0⤊ 0⤋

i always hate proving they are crazy and are not needed! even always they forgoten very soon

2007-01-03 18:05:33 · answer #2 · answered by arman 1 · 0⤊ 2⤋