Problem E : 6700 , page 413 , GMB 11/1979

From GAZETA MATEMATICA , series B :

ANSWER CiP

diagonals = a and a\sqrt{2}

4-th side = 0,5a(\sqrt{6}-\sqrt{2})

SOLUTION   CiP

The figure for the problem is as follows:

The hypothesis and conclusion :

For calculating the diagonals