If the two sides of an isosceles triangle are 4 cm and 8 cm long, what is its perimeter in cm?
一个等腰三角形的两条边分别长4厘米和8厘米，它的周长是多少厘米．
<gadget id="calculator">8 + 8 + 4</gadget>
<output>20</output>

<result>20</result>