******************** Exercise 2 **************************** *
Implement a Matrix class for 2-by-2 matrices 


Include a default constructor, a copy constructor, an inverse() 
function that returns the inverse of the matrix, a det() function 
that returns the determinant of the matrix, a Boolean function isSingular() 
that returns 1 or 0 according to whether the determinant is zero, 
and a print() function that returns the  elements of the matrix

******************** Exercise 2 **************************** *

Implement a "Complex" class, which represents complex numbers.
The data members are the real and imaginary part of the number.
There must be a constructor composed by 2 double.
Overload the operators +, -, *, =, ==,! =, <<, >>
N. B .: the functions that overload the operators << and >> 
must be declares as "friend" function

Execution example:
./usaComplessi.exe
Give me a complex number in the form: a + bi
3 + 5i

x: 0 + 0i
y: 4.3 + 8.2i
z: 3.3 + 1.1i
k: 3 + 5i

x = y + z:
7.6 + 9.3i = 4.3 + 8.2i + 3.3 + 1.1i

x = y - z:
1 + 7.1i = 4.3 + 8.2i - 3.3 + 1.1i

x = y * z:
23.21 + 31.79i = 4.3 + 8.2i * 3.3 + 1.1i

23.21 + 31.79i ! = 3 + 5i

3 + 5i == 3 + 5i



******************** Exercise 3 **************************** *

Implement a Vector class that represents vectors in 3 dimensions
(hint: use 3-component representation)
The class must have at least:
- a constructor with 3 double
- overloading of the operators <<, +, -
- the operation "scalar product" 
- member functions that return the components and the form of the vector

Write a simple program that creates and uses objects of the Vector class

Execution example:
./useVettore.exe
 Vector v1 (1, 0, 0)
 Vector v2 (1, 1, 0)

 Vector v (2, 1, 0) sum of v1 vectors (1, 0, 0) and v2 (1, 1, 0)
 component x: 2
 component y: 1
 component z: 0
 form of v: 2.23607

 The scalar product of (1, 0, 0) and v2 (1, 1, 0): 1