User talk:134.157.64.73

Hi, I was trying to use the formulas in the Wikipedia page for 'Square root of a 2 by 2 matrix' and wasn't able to calculate the root correctly with the formula as provided. In another reference I found a slightly different formula that works correctly.

I'm not comfortable changing the Wikipedia page, but if you concur that it is an error than perhaps you'd be willing to update the page.

Here is the text from the page that I'm concerned about:

where A, B, C, and D may be real or complex numbers. Furthermore, let τ = A + D be the trace of M, and δ = AD − BC be its determinant. Let s be such that s2 = δ, and t be such that t2 = τ + s. That is, {\displaystyle s=\pm {\sqrt {\delta }},\qquad t=\pm {\sqrt {\tau +s}}.}{\displaystyle s=\pm {\sqrt {\delta }},\qquad t=\pm {\sqrt {\tau +s}}.}

The two equations for t are currently:

a) t2 = τ + s

b) t=\pm {\sqrt {\tau +s}}

And I think that they should be:

a) t2 = τ + 2s

b) t=\pm {\sqrt {\tau +2s}}

Sincerely, David

Yes, I indeed made a mistake. I edited the page which now displays the correct formula.