SOLUTION: Prove cos(x+pi) is equivalent to -cos(x). Thanks

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Question 974506: Prove cos(x+pi) is equivalent to -cos(x). Thanks
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Prove cos(x+pi) is equivalent to -cos(x)
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cos(x+pi) = cos(x)*cos(pi) - sin(x)*sin(pi)
= cos(x)*(-1) - sin(x)*0
= -cos(x)