If a semicircle has an arc length of 3.14 decimeters, what is the diameter in decimeters?
一个半圆形，已知弧长3.14分米，那么直径长多少分米．
<gadget id="calculator">2 / 3.14</gadget>
<output>0.636943</output>

<gadget id="calculator">3.14 * 0.636943</gadget>
<output>2.000001</output>

<result>2.000001</result>