【c语言】(函数)利用麦克劳林公式求sinx，cosx，tanx

- 日理万妓 2022-04-15 07:06 684阅读 0赞

#### 题目： ####

> 求tanx，已知麦克劳林公式![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hhbG9fNzc3Nzc3Nw_size_16_color_FFFFFF_t_70]

#### 思路分析： ####

1.  先设定两个函数，一个pwr算乘方或者用\#include<math.h>的pow（）来计算，另一个fac算阶乘
2.  利用循环，将sinx和cosx依据麦克劳林公式代入上述两个函数中即可求出
3.  tanx = sinx/cosx

***注意：x的0次方为1，0和1的阶乘为1***

#### 代码实现： ####

#include<stdio.h>
    float pwr(float x, int n)
    { 
     int i = 0;
     float powers = 1;
    // printf("n = %d\n",n);
     if(n == 0)
     { 
    // printf("yes\n");
      return 1;
     }
     for(i = 1; i <= n; i++)
     { 
      powers = powers * x;
     }
    // printf("power = %f\n",powers);
     return powers;
    }
    int fac(int n)
    { 
        int i = 0;
        float pdt = 1;
     if(n == 0 || n == 1)
     { 
    // printf("yes\n");
      return 1; 
     }
     for(i = 2; i <= n; i++)
     { 
      pdt = pdt * i;
     }
    // printf("pdt = %f\n",pdt); 
     return pdt;
    }
    int main()
    { 
     int k = 0, i = 0, j = 0, cons = 1; 
     float x = 0, s = 0, c = 0, sin = 0, cos = 0, tan = 0, y = 0;     //用y将弧度制转换为角度制 
     const float pi = 3.1415926;
     printf("Input the angle:"); 
     scanf("%f",&y);
     x = y*pi/180;
     for(k = 1; k <= 11; k++)
     { 
      i = 2 * k - 1;
      j = 2 * k - 2;
      s = cons*pwr(x,i)/fac(i);
      c = cons*pwr(x,j)/fac(j);
      cons = -1*cons;
    // printf("cons = %d\n",cons);
         sin = sin + s;
         cos = cos + c;
        }
        tan = sin/cos;
     printf("sin(%.0f) = %f cos(%.0f) = %f tan(%.0f) = %f",y,sin,y,cos,y,tan);
     return 0; 
    }

#### 运行结果： ####

如要求tan45°  
![在这里插入图片描述][20181122214802422.png]

#### 附加： ####

代码中注释掉的printf是用在debug程序的时候

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0hhbG9fNzc3Nzc3Nw_size_16_color_FFFFFF_t_70]: /images/20220415/1e44adb88893483ea711ae8e751d3990.png
[20181122214802422.png]: /images/20220415/ff04382fefbb4d208caa465e3510a0f2.png