The three interior angles of a triangle are all 60°. It is known that the length of one side is 13 cm. What is the perimeter of the triangle in cm?
一个三角形的三个内角都是60°，已知其中的一条边长度是13厘米，求这个三角形的周长是多少厘米？
<gadget id="calculator">13 * 3</gadget>
<output>39</output>

<result>39</result>