Proving a = a^-1 implies a^2 = e in group theory

mehrts
Messages
15
Reaction score
0
Let G be a group. Let 'a' be an element of G. Let e be the identity of G Prove that if a = a^-1 then a^2= e.

Is the proof below correct ?
Suppose a = a^-1. Then

a^2 = aa = a(a^-1) = e.
 
Physics news on Phys.org
yeah, if a is it's own inverse then a^2 is e. your proof looks fine to me.
 
Thxs. He he he :!)
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top