cschwan
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 Nov5 accepted Definition of unitary operators Nov5 comment Definition of unitary operators Thanks for your proof and particular nice example. Is $V^* (x_n)=(y_n), y_n=x_{n+1}$? Then I also see why $V V^*=1$, but $V^* V \neq 1$! Nov5 asked Definition of unitary operators Jan31 awarded Scholar Jan31 accepted Calculating a limit with constraints Jan29 comment Calculating a limit with constraints It is weird why my numerical answer differs from your analytical answers (is there maybe a third limit?). With $x=y=10^{-10}, z=1, w=-\sqrt{2 \cdot 10^{-20} + 1^2}$ and 4096 bits precision I still obtain about $1 + i$. Jan29 awarded Supporter Jan29 comment Calculating a limit with constraints Thanks for your reply! Maybe it helps if I explain a bit of the context. The formula is used in a numerical program and obviously it is not defined for $(x,y,z,w) = (0,0,-z,z)$. Now my questions basically is: What do I do in this case (there is data that has exactly this form). And now that we have two limits, which one do I choose? Jan29 revised Calculating a limit with constraints added 2 characters in body Jan29 awarded Student Jan29 comment Calculating a limit with constraints $z$ is a fixed real number and may be negative. If it helps, the denominator is $\sqrt{|w+z|}$. Jan29 revised Calculating a limit with constraints deleted 8 characters in body Jan29 revised Calculating a limit with constraints added 25 characters in body Jan29 comment Calculating a limit with constraints I am really sorry, you're right. I hope my question makes sense now. Jan29 revised Calculating a limit with constraints deleted 1 characters in body Jan29 awarded Editor Jan29 revised Calculating a limit with constraints added 99 characters in body Jan29 asked Calculating a limit with constraints