#include 
#include 

double area(double va, double vb, double vc);

main ()
{
	double a, b, c;

	printf("Enter value of a> ");
	scanf("%lf", &a);
	printf("Enter value of b> ");
        scanf("%lf", &b);
	printf("Enter value of c> ");
        scanf("%lf", &c);


	printf("Values of a is %f \n", a);
	printf("Values of b is %f \n", b);
	printf("Values of c is %f \n", c);
	printf("Area of triangle is %f \n",area(a, b, c));
}

double
area(double va, double vb, double vc)
{
	double s; /* local variable */
	s = (va + vb + vc)/2;
	return(sqrt(s*(s-va)*(s-vb)*(s-vc)));
}

    Source: geocities.com/yosemite/rapids/9568

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