There is a kind of small colored flag on the venue to celebrate "Six, First". The shape of the small colored flag is an isosceles triangle. The top angle of the small colored flag is 40°. How many degrees is its bottom angle?
庆祝"六、一"会场上有一种小彩旗的形状是等腰三角形，小彩旗的顶角是40°，它的底角是多少度？
<gadget id="calculator">180 - 40</gadget>
<output>140</output>

<gadget id="calculator">140 / 2</gadget>
<output>70</output>

<result>70</result>