When deriving the formula for the area of a circle, divide the circle into several parts on average and put together an approximate rectangle. If the length and width of the rectangle are 12.56cm and 4cm respectively, what is the area of the circle?
在推导圆的面积公式时，将圆平均分成若干份，拼成一个近似的长方形，如果这个长方形的长和宽分别是12.56cm和4cm，这个圆的面积是多少．
<gadget id="calculator">12.56 * 4</gadget>
<output>50.24</output>

<result>50.24</result>