All the sides of a square are of the same measure and also all the interior angles of a square are of 90º measure. Therefore, the given square READ can be drawn as follows.

(1)A rough sketch of this square READ can be drawn as follows.

(2) Draw a line segment RE of 5.1 cm and an angle of 90º at point R and E.

(3) As vertex A and D are 5.1 cm away from vertex E and R respectively, cut line segments EA and RD, each of 5.1 cm from these rays.

(4) Join D to A.

READ is the required square.