Question 1209041
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<pre>

x-coordinate of the midpoint is half of the sum of x-coordinates of the given points

    x = {{{(1/2)*((a+b)/2 + (a-b)/2))}}} = 0.5a.



y-coordinate of the midpoint is half of the sum of y-coordinates of the given points

    x = {{{(1/2)*((c+d)/2 + (c-d)/2)}}} = 0.5c.


Thus the midpoint is  (x,y) = (0.5a,0.5c).    <U>ANSWER</U>
</pre>

Solved.