Given that the base angle of an isosceles triangle is 40°, what is the apex angle in °°?
已知一个等腰三角形的底角是40°，它的顶角是多少°°．
<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<gadget id="calculator">180 - 80</gadget>
<output>100</output>

<result>100</result>