semicircular piece of iron has a perimeter of 5.14 decimeters, what is the area in square decimeters?
一个半圆形铁片，周长是5.14分米，面积是多少平方分米．
<gadget id="calculator">3.14 + 2</gadget>
<output>5.14</output>

<gadget id="calculator">5.14 / 5.14</gadget>
<output>1</output>

<gadget id="calculator">1 ** 2</gadget>
<output>1</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3.14 * (1/2)</gadget>
<output>1.57</output>

<result>1.57</result>