The value of cos4π8+cos43π8+cos45π8+cos47π8 is

Question

The value of

\cos^{4} \frac{π}{8} + \cos^{4} \frac{3 π}{8} + \cos^{4} \frac{5 π}{8} + \cos^{4} \frac{7 π}{8}

\frac{3}{2}

\frac{1}{2}

\frac{3}{4}

\frac{1}{4}

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