Let D =(adsbygoogle = window.adsbygoogle || []).push({});

[d11 d12]

[d21 d22]

be a 2x2 matrix. Prove that D commutes with all other 2x2

matrices if and only if d12 = d21 = 0 and d11 = d22.

I know if we can prove for every A, AD=DA should be true, but I really dont know how to proceed from there. I tried equating elements of AD with DA but that really didnt help.

Can anyone help me with this problem. Thanks..

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Commutation property

**Physics Forums | Science Articles, Homework Help, Discussion**