The school makes a safety notice board of an isosceles triangle with a vertex angle of 100°, what is the degree of one of the bottom angles?
学校做一块顶角是100°的等腰三角形安全提示牌，那么其中一个底角的度数是多少°．
<gadget id="calculator">180 - 100</gadget>
<output>80</output>

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

<result>40</result>