A rope is used to form an isosceles triangle whose top angle is 80°, what is the base angle?
用一条绳子围成一个顶角是80°的等腰三角形，它的一个底角是多少度？
<gadget id="calculator">180 - 80</gadget>
<output>100</output>

<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<result>50</result>