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Is my proof correct for lim_(n-> infty) |z_n| = |z| ? Complex Analysis
Show that if lim_{n-> infty} z_n = z
then
lim_{n-> infty} |z_n| = |z|
Is this correct:
lim_{n-> infty} |z_n| = |z|
iff
Assume that the conditions hold;
lim_{n-> infty} |x_n| = |x| and lim_{n-> infty} |y_n| = |y|
According to these conditions there exist, for each positive number \epsilon, positive integers n_1 and n_2 such that:
||x_n| - |x|| < epsilon/2 whenever n > n_1
and
||y_n| - |y|| < epsilon/2 whenever n > n_2
Hence, if n_0 is the larger of the two integers n_1 and n_2
||x_n| - |x|| < epsilon/2 and ||y_n| - |y|| < epsilon/2 whenever n > n_0
Since
|(|x_n| + i|y_n|) - (|x| + i|y|) =
|(|x_n| - |x|) + i(|y_n|-|y|) <= ||x_n| - |x|| + ||y_n| - |y||
Then
||z_n| - |z|| < epislon/2 + epsilon/2 = epsilong whenver n > n_0
Thus it holds that
lim_(n-> infty) |z_n| = |z| because for every epsilon > 0 there exists N > 0 such that | |z_n| - |z|| < epsilon
I am using a proof from the textbook to draw this from so just wanted to check to see if I've left anything out and if it makes sence!
Thanks
Homework Statement
Show that if lim_{n-> infty} z_n = z
then
lim_{n-> infty} |z_n| = |z|
Homework Equations
The Attempt at a Solution
Is this correct:
lim_{n-> infty} |z_n| = |z|
iff
Assume that the conditions hold;
lim_{n-> infty} |x_n| = |x| and lim_{n-> infty} |y_n| = |y|
According to these conditions there exist, for each positive number \epsilon, positive integers n_1 and n_2 such that:
||x_n| - |x|| < epsilon/2 whenever n > n_1
and
||y_n| - |y|| < epsilon/2 whenever n > n_2
Hence, if n_0 is the larger of the two integers n_1 and n_2
||x_n| - |x|| < epsilon/2 and ||y_n| - |y|| < epsilon/2 whenever n > n_0
Since
|(|x_n| + i|y_n|) - (|x| + i|y|) =
|(|x_n| - |x|) + i(|y_n|-|y|) <= ||x_n| - |x|| + ||y_n| - |y||
Then
||z_n| - |z|| < epislon/2 + epsilon/2 = epsilong whenver n > n_0
Thus it holds that
lim_(n-> infty) |z_n| = |z| because for every epsilon > 0 there exists N > 0 such that | |z_n| - |z|| < epsilon
I am using a proof from the textbook to draw this from so just wanted to check to see if I've left anything out and if it makes sence!
Thanks