SOLUTION: Prove that cos2x=cos^2x-1 What do I do to the left side to make it equal to the right side?

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Question 918888: Prove that cos2x=cos^2x-1
What do I do to the left side to make it equal to the right side?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Prove that cos2x=cos^2x-1
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cos(2x) = cos(x+x) = cos(x)*cos(x)-sin(x)*sin(x)
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= cos^2(x) - sin^2(x)
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= cos^2(x) -(1-cos^2(x))
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= cos^2(x)-1+cos^2(x)
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= 2cos^2(x) - 1
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Cheers,
Stan H.
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