Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:7:16: error: ‘x1’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:19: error: ‘x2’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:24: error: ‘y1’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:27: error: ‘y2’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:37: error: ‘x3’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:45: error: ‘y3’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:51: error: expected primary-expression before ‘...’ token 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:7:98: error: ‘modul’ was not declared in this scope 1/2*modul((x1-x2)*(y1+y2) + (x2-x3)*(y2+y3) + ... + (x(n-1)-xn)*(y(n-1)+yn) + (xn-x1)*(yn+y1)) ^ user.cpp:8:5: error: expected ‘;’ before ‘cout’ cout << "Hello world!" << endl; ^