An isosceles triangle vegetable field has a circumference of 160 meters, a waist length of 50 meters, and a height of 40 meters on the bottom edge. What is the area of this vegetable field in square meters?
一块等腰三角形菜地，周长160米，腰长50米，底边上的高40米，这块菜地的面积是多少平方米？
<gadget id="calculator">160 - 50 - 50</gadget>
<output>60</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">60 * 20</gadget>
<output>1_200</output>

<result>1_200</result>