What is the base angle of an isosceles triangle whose apex angle is 50°?
顶角是50°的等腰三角形，它的一个底角是多少度．
<gadget id="calculator">180 - 50</gadget>
<output>130</output>

<gadget id="calculator">130 / 2</gadget>
<output>65</output>

<result>65</result>