Proving the Group Properties of M, the Set of Nth Roots of Unity

ustus
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Hello,
Please help in solving the four set of problems, i will be very happy explaining comment as really want to understand.
The problem will spread to the extent of understanding preduduschey.

1 Problems:

The set M, M = {e^(j*2*pi*k/n) , k= 0,1,2...n-1} denotes the set of the nth roots of unity,
i.e. the solution set of z^n = 1 for fixed n.
Show that M, together with multiplication of complex numbers, forms a group.
 
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ustus said:
Hello,
Please help in solving the four set of problems, i will be very happy explaining comment as really want to understand.
The problem will spread to the extent of understanding preduduschey.

1 Problems:

The set M, M = {e^(j*2*pi*k/n) , k= 0,1,2...n-1} denotes the set of the nth roots of unity,
i.e. the solution set of z^n = 1 for fixed n.
Show that M, together with multiplication of complex numbers, forms a group.

Ok. To show something is a group, what four things do you need to show?

Which one(s) are you stuck on?
 
Are the following evidence to the problem?
 

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