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2_14855_1048814_29865.cpp
2_14855_1048814_29865.cpp(6) : error C2668: “acos” : 对重载函数的调用不明确
        \include\math.h(586): 可能是“long double acos(long double)”
        \include\math.h(538): 或       “float acos(float)”
        \include\math.h(183): 或       “double acos(double)”
        试图匹配参数列表“(int)”时