Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:44:20: error: expected ‘)’ before ‘x1’ x1[j]*y2[j]+x2[j]*y11[i]+y11[j]*x1[i]-y2[j]*x1[i]-y11[i]*x1[j]-x2[j]*y11[j]==0 ^ user.cpp:13:20: warning: unused variable ‘a1’ [-Wunused-variable] double a,b,c,d,a1,b1,c1,d1; ^ user.cpp:13:23: warning: unused variable ‘b1’ [-Wunused-variable] double a,b,c,d,a1,b1,c1,d1; ^