计算三角形面积

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/*
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功能：计算三角形面积
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日期：2013-06-08
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*/
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#include<stdio.h>
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#include<stdlib.h>
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#include<math.h>
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double countAreaOfTtriangle (double a,double b,double c);
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int main(void)
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{
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   double a,b,c,area;
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   printf("请输入三角形三条边的边长：");
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   scanf("%lf%lf%lf",&a,&b,&c);
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   area = countAreaOfTtriangle(a,b,c);
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   printf("该三角形的面积为：%.3lf",area);
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   system("pause");
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}
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double countAreaOfTtriangle (double a,double b,double c)
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{
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  double Area,s;
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    if(a+b>c && a+c>b && c+b>a)
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  {
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      s = ( a + b + c ) / 2.0 ;
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    Area = sqrt(s*(s-a)*(s-b)*(s-c));
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    return Area;
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  }
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  else
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  {
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    return -1.0;
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  }
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}