Eroare de compilare: user.cpp: In function ‘double a2(int, int, int, int, int, int)’: user.cpp:20:33: error: ‘y2’ was not declared in this scope {int p=x1*y4+x4*y3+x4*y1-x3*y2-x1*y3-x4*y1; ^ user.cpp: In function ‘int main()’: user.cpp:40:30: error: ‘x4’ was not declared in this scope fin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4; ^ user.cpp:40:34: error: ‘y4’ was not declared in this scope fin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4; ^ user.cpp:41:7: error: invalid operands of types ‘double(int, int, int, int, int, int)’ and ‘double(int, int, int, int, int, int)’ to binary ‘operator+’ s+=a1+a2+a3; ^ user.cpp:42:7: error: ISO C++ forbids comparison between pointer and integer [-fpermissive] if(a==s) ^