C算法--入门 2.2

绝地灬酷狼 2021-10-26 11:32 235阅读 0赞

常用math函数

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
    2 #include <math.h>
    3 
    4 /*绝对值*/
    5 int main(){
    6     double db=-12.56;
    7     printf("%.2f\n",fabs(db));
    8     return 0;
    9 }

fabs(dhouble x)绝对值

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
     2 #include <math.h>
     3 
     4 /*向下(floor)向上(ceil)取整*/
     5 int main(){
     6     double db1=-5.2,db2=5.2;
     7     printf("%.0f %.0f\n",floor(db1),ceil(db1));
     8     printf("%.0f %.0f\n",floor(db2),ceil(db2));
     9     return 0;
    10 }

floor/ceil取整

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
    2 #include <math.h>
    3 
    4 /*2的三次方*/
    5 int main(){
    6     double db =pow(2.0,3.0);
    7     printf("%f\n",db);
    8     return 0;
    9 }

pow次方

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
    2 #include <math.h>
    3 
    4 /*算术平方根*/
    5 int main(){
    6     double db=sqrt(2.0);
    7     printf("%f\n",db);
    8     return 0;
    9 }

sqrt算术平方根

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

#include <stdio.h>
    #include <math.h>
    
    /*返回double类型以自然数为底的对数*/
    int main(){
        double db=log(1.0);
        printf("%f\n",db);
        return 0;    
    }

log

注：C中没有对任意底求对数的函数，用换底公式logzb=logeb/logez

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
     2 #include <math.h>
     3 
     4 /*弧度制*/
     5 /*acos是一个函数,其功能是求反余弦。acos(-1.0)就是求-1.0的反余弦,再赋值给double类型的常变量pi*/
     6 const double pi=acos(-1.0);
     7 
     8 int main(){
     9     /*   PI*一次旋转的角度数/180  */
    10     double db1=sin(pi*45/180);
    11     double db2=cos(pi*45/180);
    12     double db3=tan(pi*45/180);
    13     printf("%f,%f,%f\n",db1,db2,db3);
    14     return 0;
    15 }

三角函数弧度制

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
     2 #include <math.h>
     3 
     4 /*反三角函数*/
     5 int main(){
     6     double db1=asin(1);
     7     double db2=acos(-1.0);
     8     double db3=atan(0);
     9     printf("%f,%f,%f\n ",db1,db2,db3);
    10     return 0;
    11 }

反三角函数

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <stdio.h>
     2 #include <math.h>
     3 
     4 int main(){
     5     double db1=round(3.40);
     6     double db2=round(3.45);
     7     double db3=round(3.50);
     8     double db4=round(3.55);
     9     double db5=round(3.60);
    10     printf("%d, %d, %d, %d ,%d\n",(int)db1,(int)db2,(int)db3,(int)db4,(int)db5);
    11     return 0;
    12 }

round四舍五入

转载于:https://www.cnblogs.com/Catherinezhilin/p/11131446.html

[ContractedBlock.gif]: https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20211026/22a4c6628df84fe5ae513911f6720086.png