Copyright © University of Cambridge. All rights reserved.
'Bend' printed from https://nrich.maths.org/
Work out the length of the straight line at an angle $\theta$ say
to one wall which just touches the inner corner in terms of $a,\ b$
and $\theta$. This length will change as $\theta$ changes and it
won't be possible to manoeuvre an object around the corner which is
longer then the minimum value of this length.