Question 477553
<pre>
You just need the midpoint formula, which just tells us
to average the two x-coordinates and average the two y-coordinates.

In other words, the midpoint between the two points 

{{{(matrix(1,3,

x[1],",",y[1]))}}} and {{{(matrix(1,3,

x[2],",",y[2]))}}} 

is given by {{{(matrix(1,3,

(x[1]+x[2])/2,",", (y[1]+y[2])/2))}}}

So to find the midpoint of diagonal EG, it is the midpoint between

{{{(matrix(1,3,-1,",",2))}}} and {{{(matrix(1,3,7,",",-1))}}} and is given by

{{{(matrix(1,3,(-1+7)/2,",", (2+(-1))/2))}}} = {{{(matrix(1,3,6/2,",", 1/2))}}} = {{{(matrix(1,3,3,",",1/2))}}}.

As a check, also find the midpoint of diagonal FH, which is the midpoint
between {{{(matrix(1,3,2,",",4))}}} and {{{(matrix(1,3,4,",",-3))}}} and is given by {{{(matrix(1,3,(2+4)/2,",", (4+(-3))/2))}}} = {{{(matrix(1,3,6/2,",", 1/2))}}} = {{{(matrix(1,3,3,",",1/2))}}}.

They turn out to be the same point, so {{{(matrix(1,3,3,",",1/2))}}} is the correct midpoint.

Edwin</pre>