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Math pre cal

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prove the following identity
cos^4X - sin^4X = 1-2sin^2X

  • Math pre cal -

    LS = (cos^2x + sin^2x)(cos^2x - sin^2x)
    = 1((1-sin^2x) - sin^2x)
    = 1 - 2sin^2x
    = RS

  • Math pre cal -

    Factorize the left hand side using:
    A²-B²=(A+B)(A-B)
    or
    A4-B4 = (A²+B²)(A²-B²)

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