Gaokao Math Practice Question
4. (5 分) 已知 $\sin a-\cos a=\frac{4}{3}$, 则 $\sin 2 a=(\quad)$
- A.$-\frac{7}{9}$
- B.$-\frac{2}{9}$
- C.$\frac{2}{9}$
- D.$\frac{7}{9}$
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