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Itel

  • 3 years ago

Help please Verify the identity. cos 4x + cos 2x = 2 - 2 sin^2 2x - 2 sin^2 x

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  1. shining
    • 3 years ago
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    cos 4x = 2cos^2 2x - 1 cos 2x = 2cos^2 x -1 result:2-2sin^ 2x - 2sin^2 x

  2. Itel
    • 3 years ago
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    so 2cos^2 2x - 1 + 2cos^2 2x - 1= 2-2sin^ 2x - 2sin^2 x?

  3. asnaseer
    • 3 years ago
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    do you know how to express \(\cos(2x)\) in terms of \(\sin(x)\)?

  4. asnaseer
    • 3 years ago
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    using the double-angle formulae

  5. shining
    • 3 years ago
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    yes , you should first optimize it wheter you know double angle formulas or not?

  6. Itel
    • 3 years ago
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    so am I right then? That so 2cos^2 2x - 1 + 2cos^2 2x - 1= 2-2sin^ 2x - 2sin^2 x?

  7. shining
    • 3 years ago
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    yes , it was great

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