The midpoint of a line divides the line into equal segments.
See below for the proof of 
The given parameters are:



The coordinates of M (midpoint of AB) are calculated as follows:
So, we have:



The coordinates of N (midpoint of BC) are calculated as follows:
So, we have:



Distance MN is:

So, we have:


Distance AC is calculated as follows:

So, we have:


Split

Take positive square root of 4

To prove that:

We have:


The above equation is true.
Hence. 
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