Given that the apex angle of an isosceles triangle is 60°, what is the base angle of this isosceles triangle?
已知一个等腰三角形的顶角是60°，这个等腰三角形的底角是多少度？
<gadget id="calculator">180 - 60</gadget>
<output>120</output>

<gadget id="calculator">120 / 2</gadget>
<output>60</output>

<result>60</result>