Try to solve a quartic equation
in [Math]
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From: Wood on 1 Aug 2010 00:51 Thank you so much....I need to check what I was doing wrong in my calculating.... Now, more important is what is a "principal" square root for a complex number? sqrt(-1 + 2i) = 0.786151377814533 + 1.27201964947877i , or -0.786151377928752 - 1.27201964940818i How to determine which is the "principal" square root?
From: Ray Vickson on 1 Aug 2010 05:43 On Aug 1, 1:51 am, Wood <wood0...(a)sohu.com> wrote: > Thank you so much....I need to check what I was doing wrong in my calculating.... > Now, more important is what is a "principal" square root for a complex number? It is the one having a positive real part (except for the case of z = - |real|, where the principal square root is i*sqrt(|real|). Basically, if you use a polar representation z = r*exp(i*t), with r > 0 and -pi < t <= pi, the principal square root is sqrt(r)*exp(i*t/2). Note that if z =/= -|real|, we have -pi < t < pi, hence cos(t/2) > 0, meaning that we have a positive real part. R.G. Vickson > sqrt(-1 + 2i) = 0.786151377814533 + 1.27201964947877i , or -0.786151377928752 - 1.27201964940818i > How to determine which is the "principal" square root?
From: Wood on 1 Aug 2010 23:42
I think I can finish the program now. Thanks a lot for your helps. |