Cut out the largest circle on a piece of rectangular paper with a length of 9 cm and a width of 6 cm. What is the radius of this circle?
在一张长9厘米，宽6厘米的长方形纸上剪一个最大的圆，这个圆的半径是多少．
<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<result>3</result>