What is the base angle of an isosceles triangle with a vertex angle of 58°?
一个等腰三角形，顶角58°，底角是多少．
<gadget id="calculator">180 - 58</gadget>
<output>122</output>

<gadget id="calculator">122 / 2</gadget>
<output>61</output>

<result>61</result>