使用时注意类型，可见两者皆不可以用int

1.pow

函数声明：

     double pow (double base     , double exponent);      float pow (float base      , float exponent);long double pow (long double base, long double exponent);     double pow (double base     , int exponent);long double pow (long double base, int exponent);

2.sqrt

函数声明：

 double sqrt (double x);      float sqrt (float x);long double sqrt (long double x);