include

include

double main()
{
double a,b,c,size,area;
a=3.1;
b=4.1;
c=5.1;
size=area(a,b,c);
printf("the size of this triangle is:%lf\n",size);
return 0;
}
double area(double a,double b,double c)
{
double area,s;
s=(a+b+c)/2;
area=sqrt(s*(s-a)*(s-b)*(s-c));
return area;
}

error C2064: term does not evaluate to a function这是错误信息，希望大神指导

double main()
->
int main()

在int main上面加上
double area(double a,double b,double c);

double a,b,c,size,area;
->
double a,b,c,size;

 # include <stdio.h>
# include <math.h>
double area(double a,double b,double c);
int main()
{
double a,b,c,size;
a=3.1;
b=4.1;
c=5.1;
size=area(a,b,c);
printf("the size of this triangle is:%lf\n",size);
return 0;
}
double area(double a,double b,double c)
{
double area,s;
s=(a+b+c)/2;
area=sqrt(s*(s-a)*(s-b)*(s-c));
return area;
}

the size of this triangle is:6.354173

#include
#include
double ar(double a,double b,double c)
{
double area,s;
s=(a+b+c)/2;
area=(s*(s-a)*(s-b)*(s-c));
return area;
}
int main()
{
double a,b,c,size,area;
a=3.1;
b=4.1;
c=5.1;
size=ar(a,b,c);
printf("the size of this triangle is:%lf\n",size);
return 0;
}
把你的函数名和定义的变量名区别开,应该是在main里面定义的area把 函数area给顶替了.所以你原来的程序area不是一个函数, main前面要写成int

头文件的加上math.h