A sector has a radius of 5 cm and an area of 15.7 square centimeters. What is the central angle of this sector?
一扇形的半径5厘米，面积15.7平方厘米，这个扇形的圆心角是多少．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<gadget id="calculator">15.7 / 78.5</gadget>
<output>0.2</output>

<gadget id="calculator">0.2 * 360</gadget>
<output>72</output>

<result>72</result>