If the apex angle of an isosceles triangle is 40°, what is the measure of each base angle?
一个等腰三角形的顶角是40°，每个底角是多少度．
<gadget id="calculator">180 - 40</gadget>
<output>140</output>

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

<result>70</result>