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高中数学必修 第一册（648题）
已知
知识点：第五章 三角函数
参考答案：\(\because f\left ( {α} \right )=\frac {\cos {\left ( {\frac {\pi } {2}+α} \right )\sin {\left ( {α-\frac {\pi } {2}} \right )}}} {\cos {\left ( {-\pi -α} \right )\tan {\left ( {\pi -α} \right )}}}=\frac {\left ( {-\sin {α}} \right )\left ( {-\cos {α}} \right )} {\left ( {-\cos {α}} \right )\left ( {-\tan {α}} \right )}=\cos {α}\)
\(\therefore f\left ( {\frac {2017\pi } {3}} \right )=\cos {\left ( {672\pi +\frac {\pi } {3}} \right )}=\cos {\frac {\pi } {3}}=\frac {1} {2}\)