A square has a diagonal of 4 decimeters, what is the area of the square in square decimeters?
一个正方形，对角线长4分米，这个正方形的面积是多少平方分米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<result>8</result>