Prove that cos 6A - 2 cos 4A - cos 2A + 2 = 32 sin⁴ A cos² A ?

Identity trigonometry.

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  • Indica
    Lv 7
    2 years ago
    Favorite Answer

    cos(6A)−cos(2A) = −2sin(2A)sin(4A) = −4sin²(2A)cos(2A) and 2−2cos(4A) = 4sin²(2A)

    ∴ LHS = 4sin²(2A)(1−cos(2A)) = 4(4sin²Acos²A)(2sin²A) = 32sin⁴Acos²A

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