Question 394503
It is known that
The sum of the interior angles of a "n" sided polygon is =(n-2)*180
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assuming that all the interior angles are equal, then a single interior angle will measure (n-2)*180/n
==
Since you state that the interior angle is 90 then
(n-2)*180/n=90
180n-360=90n
90n=360
n=4