math.h

1.求余

extern double fmod(double,double);

fmod(10.2,3) =1.2

2.四舍五入

extern double round(double);

round(10.5) =11

3.平方

extern double pow(double,double);

pow(3,4)＝81

4.开方

extern double sqrt(double);

sqrt(16) =4

5.自然数 e ^ n

extern double exp(double);

exp(3) = pow(2.718281828,3) =20.085537

6.对数

extern double log(double);   // e为底

extern double log10(double); // 10为底

log(20.085537) ＝3

log10(100) =2

5.绝对值

extern double fabs(double);

fabs(-10) =10

6.取整

extern double ceil(double); //向上

extern double floor(double);//向下

ceil(10.2) =11

floor(10.2) =10

7.求斜边

extern double hypot(double,double); //直角三角形两直边

hypot(3,4) =5

8.计算 x *2 ^ n

extern double ldexp(double,int);

ldexp(3,4)＝3 *2 ^ 4 = 48