Pre-Calculus Homework Help!!
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Pre-Calculus Homework Help!!

[From: ] [author: ] [Date: 12-04-09] [Hit: ]
......
Verify the identity:
cos(x+y) + cos(x-y) = 2cosxcosy

This is one of the last problems to my homework and I am having extreme difficulty understanding it. If you could please make your answer as simple to understand, I will greatly appreciate it! Thanks for the help! :)

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Cos[x + y] + Cos[x - y] = 2 Cos[x] Cos[y]

Cos[x] Cos[y] - Sin[x] Sin[y] + Cos[x - y] = 2 Cos[x] Cos[y]

Cos[x] Cos[y] - Sin[x] Sin[y] + Cos[x] Cos[y] + Sin[x] Sin[y] = 2 Cos[x] Cos[y]

2 Cos[x] Cos[y] = 2 Cos[x] Cos[y]
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