In an isosceles triangle, its apex angle is 40°, what is the measure of its base angle?
在一个等腰三角形中，它的顶角是40°，它的底角的度数是多少．
<gadget id="calculator">180 - 40</gadget>
<output>140</output>

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

<result>70</result>