The base angle of an isosceles triangle is 80°, what is the apex angle?
一个等腰三角形的底角是80°，顶角是多少°
<gadget id="calculator">80 * 2</gadget>
<output>160</output>

<gadget id="calculator">180 - 160</gadget>
<output>20</output>

<result>20</result>