I am okay with getting the that the first arg equation describes the arc of a circle, but i am a bit stuck on how to interpret the next part.Show that in an Argand diagram the equation

$\displaystyle \arg (z-2) - \arg (z-2i) = \frac{3 \pi}{4}$

represents an arc of a circle and that $\displaystyle \frac{|z-4|}{|z-1|}$ is constant on this circle.

Find values of z corresponding to the points in which the circle is cut by the curve given by

$\displaystyle |z-1| + |z-4| = 5$

anyone willing to give me a hand?

thanks, Bobak