数学试题讲解

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若

α \in (\frac{π}{4}, \frac{3 π}{4}), 6 \tan (\frac{π}{4} + α) + 4 \cos (\frac{π}{4} - α) = 5 \cos 2 α

, 则

\sin 2 α =

\frac{24}{25}

\frac{12}{25}

\frac{7}{25}

\frac{1}{5}