Compilare: user.c: In function ‘main’: user.c:23:5: warning: implicit declaration of function ‘fabs’ [-Wimplicit-function-declaration] A=fabs((A+x1*yi-xi*y1)/2); ^ user.c:23:7: warning: incompatible implicit declaration of built-in function ‘fabs’ [enabled by default] A=fabs((A+x1*yi-xi*y1)/2); ^ user.c:10:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(Fin,"%f",&N); ^ user.c:11:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(Fin,"%f",&xi); ^ user.c:12:11: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(Fin,"%f",&yi); ^ user.c:17:15: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(Fin,"%f",&x2); ^ user.c:18:15: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(Fin,"%f",&y2); ^