Gaokao Math Practice Question
9. (5 分) 若 $\cos \left(\frac{\pi}{4}-\alpha\right)=\frac{3}{5}$, 则 $\sin 2 \alpha=(\quad)$
- A.$\frac{7}{25}$
- B.$\frac{1}{5}$
- C.$-\frac{1}{5}$
- D.$-\frac{7}{25}$
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