Please explain in detail, thank you

1.- Using the Cartesian and polar representations, show that every complex number of the form z = x + iy can be represented in a matrix form as follows:

z=r(cos()sen()sin()cos())

and that with this representation the multiplication of complex numbers is precisely matrix multiplication.

2.-Using the above representation, show that if z and c are complex numbers, and c has norm 1, then the multiplication cz is a complex number with the same norm as z, whose argument is the sum of the arguments of z and c.