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- Thread starter kasse
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- #2

cristo

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Try looking at the identity for cos(2x)

- #3

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The correct identity is (cos4x)^2 = (1+cos8x)/2 .

- #4

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Try looking at the identity for cos(2x)

You mean cos(2x) = (cosx)^2 - (sinx)^2 ?

- #5

cristo

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Science Advisor

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You mean cos(2x) = (cosx)^2 - (sinx)^2 ?

Yes, and as arunbg says, there is a factor of 1/2 missing from your given identity.

- #6

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the identity is cos^2x = (1 + cos2x)/2 is it not?

- #7

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Yes, my mistake.

- #8

cristo

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Science Advisor

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the identity is cos^2x = (1 + cos2x)/2 is it not?

One can derive this from the double angle identity for cos(2x) using further the identity that cos

- #9

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..........

Last edited:

- #10

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Nope.

[tex] \sin^{2} x=\frac{1-\cos 2x}{2} [/tex]

Daniel.

[tex] \sin^{2} x=\frac{1-\cos 2x}{2} [/tex]

Daniel.

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