Cut a circle along its diameter and measure the circumference of a part of it is 15.42 cm. What is the area of the circle?
一个圆沿直径剪开，量得其中一部分图形的周长是15.42厘米，求圆的面积是多少？
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<result>28.26</result>