Show that the construction given in the text for constructing a square equal to the difference of 2 squares is...

Show that the construction given in the text for constructing a square equal to the difference of 2 squares is correct. Here, ABCD is the larger square with side equal to "a" and PQRS is the smaller square with side equal to "b". Cut off AK=b from AB and draw KL perpendicular to AK and intersecting DC at L. With K as a center and radius KL, draw an arc meeting AD at M. Show that the square on AM is the required square.