One base angle of an isosceles triangle is 40°, what is its top angle? What kind of triangle is it? What if the top angle is 40°?
等腰三角形的一个底角是40°，它的顶角是多少度？它又是什么三角形？如果顶角是40°呢？
<gadget id="calculator">180 - 40</gadget>
<output>140</output>

<gadget id="calculator">140 / 2</gadget>
<output>70</output>

<result>70</result>