Xiao Ming drew an isosceles triangle with a vertex angle of 100°, what is its base angle?
小明画了一个顶角是100°的等腰三角形，它的一个底角是多少．
<gadget id="calculator">180 - 100</gadget>
<output>80</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<result>40</result>