If the base angle of an isosceles triangle is 66 degrees, what is the vertex angle?
一个等腰三角形底角是66度，它的一个顶角是多少度．
<gadget id="calculator">66 * 2</gadget>
<output>132</output>

<gadget id="calculator">180 - 132</gadget>
<output>48</output>

<result>48</result>