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# epsilon-delta identity watch

1. Hi,

Was just trying to prove the identity:

E_pqs.E_nrs = d_pn.d_qr - d_pr.d_qn (E is epsilon and d is delta)

however if pqs = (1,2,2) and nrs = (1,2,2) then the left hand side is equal to 0 and the right hand side is equal to 1.

What has gone wrong, or am I just being stupid?
2. (Original post by jdavi)
What has gone wrong, or am I just being stupid?
You're being stupid When a suffix is repeated, it is understood that we sum over that suffix. In this case, that suffix is s, so we can't just set s=2 (as you did).

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Updated: March 26, 2011
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