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MathNet 2010 — Part 07 Question 131

Math Olympiad Vault · MathNet 2010 — Part 07

Question 131

Express the following in closed form, as a function of $x$:

$\sin^{2}(x) + \sin^{2}(2x) \cos^{2}(x) + \sin^{2}(4x) \cos^{2}(2x) \cos^{2}(x) + \cdots + \sin^{2}\left(2^{2010} x\right) \cos^{2}\left(2^{2009} x\right) \cdots \cos^{2}(2x) \cos^{2}(x)$.