# C5v group

1. Nov 23, 2015

### chikou24i

One of the classes of the group C5v is written C=(2*C5). So why do we mean by 2*C5 and how we can know the elements of this class from this writing ?
Thanks

2. Nov 24, 2015

### DrDu

You really mean class or rather symmetry operation? I would guess that 2*C_5 means a rotation by two times 72 degrees.

3. Nov 25, 2015

### chikou24i

I mean what means the notation of the class C'=(2C5) ,where C' is a class and 2C5 are the elements of this class.

4. Nov 25, 2015

### DrDu

Where did you see this? I don't think the C' is standard notation. The 2 C$_5$ means that the class contains two elements, namely the rotations by + or - 72 degrees.

5. Nov 26, 2015

### chikou24i

So 2 C5 means : C5, C54.
Thanks you very much that's what I want to know.

6. Nov 26, 2015

### DrDu

Yes, the two are in the same class as e.g. $\sigma_v C_5 \sigma_v=C_5^4$.