Square ABCD has side AB = 39 cm. Four identical right-angled triangles form the shaded area.<br><br>Area of one triangle = 1/2 x AE x EB = 1/2 x 15 x 36 = 270 cm&sup2;<br>Total shaded area = 4 x 270 = 1080 cm&sup2;<br><br>Final Answer: 1080 cm&sup2;