9．若 $\tan \alpha=2 \tan \frac{\pi}{5}$ ，则 $\frac{\cos \left(\alpha-\frac{3 \pi}{10}\right)}{\sin \left(\alpha-\frac{\pi}{5}\right)}=$
参考答案$C$
2015 高考数学第 9 题答案解析
2015_退役省自主命题 (2015·理)
2015_退役省自主命题 (2015·理)
9．若 $\tan \alpha=2 \tan \frac{\pi}{5}$ ，则 $\frac{\cos \left(\alpha-\frac{3 \pi}{10}\right)}{\sin \left(\alpha-\frac{\pi}{5}\right)}=$