But earlier we said $ f(x) = 1 - rac{1}{2}(\cos 2x - \cos 4x) $. When $ \cos 2x = -1 $, $ \cos 4x = 1 $, so $ -1 - 1 = -2 $, multiplied by $ -rac{1}{2} $ gives $ +1 $, so $ 1 + 1 = 2 $. Yes.

Sun, 03 May 2026 08:06:44 +0000

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