Compilare: user.c: In function ‘dist’: user.c:4:5: warning: implicit declaration of function ‘sqrt’ [-Wimplicit-function-declaration] return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)); ^ user.c:4:12: warning: incompatible implicit declaration of built-in function ‘sqrt’ [enabled by default] return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)); ^ user.c: In function ‘heron’: user.c:8:12: warning: incompatible implicit declaration of built-in function ‘sqrt’ [enabled by default] return sqrt(p*(p-a)*(p-b)*(p-c)); ^ user.c: In function ‘main’: user.c:20:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lf %lf", &xA, &yA); ^ user.c:21:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lf %lf", &xB, &yB); ^ user.c:22:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lf %lf", &xC, &yC); ^