What is the Log of a Complex Variable?

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what is log of z=X+JY?

Thanks
 
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Did you try to find out what it would be??

Here.
 
We can always write x+ iy in "polar form": x+ iy= re^{i\theta} where r= \sqrt{x^2+ y^2} and \theta= arctan(y/x).

Then ln(x+ iy)= ln(re^{i\theta})= ln(r)+ i\theta. Of course, because tangent is periodic, with period \pi, ln is not a single-valued function:
ln(x+ iy)= ln(r)+ i(\theta+ n\pi) for n any integer.
 
Thanks
 
ln(x+iy)=ln(r)+i(θ+2*nπ) for n any integer.
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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