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#4afeb14b-c117-4e4a-943a-e986ac96d76f入门选择题余弦函数与正切函数三角函数与三角恒等变换

特殊角的余弦值

cos(π3)=\cos\left(-\dfrac{\pi}{3}\right) =(  )

A. A. 12\dfrac{1}{2}
B. B. 12-\dfrac{1}{2}
C. C. 32\dfrac{\sqrt{3}}{2}
D. D. 32-\dfrac{\sqrt{3}}{2}