The red scarf is an isosceles triangle, its top angle is 120°, how much is one of its base angles?
红领巾是一个等腰三角形，它的顶角是120°，它的一个底角是多少度？
<gadget id="calculator">180 - 120</gadget>
<output>60</output>

<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<result>30</result>