If the perimeter of an isosceles triangle is 28 cm and the base is 10 cm, what is the length of the waist in cm?
如果一个等腰三角形的周长为28厘米，底为10厘米，那么腰长是多少厘米．
<gadget id="calculator">28 - 10</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<result>9</result>