A fan-shaped pool has a radius of 5 meters and an arc length of 6.28 meters. What is the area of the pool in square meters?
扇形水池半径为5米，弧长6.28米，这个水池的面积是多少平方米．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">2 * 3.14 * 5</gadget>
<output>31.4</output>

<gadget id="calculator">6.28 / 31.4</gadget>
<output>0.2</output>

<gadget id="calculator">3.14 * 25 * 0.2</gadget>
<output>15.7</output>

<result>15.7</result>