In an isosceles triangle, if a vertex angle is known to be 78°, how much is its base angle?
一个等腰三角形中，已知一个顶角是78°，求它的底角是多少度？
<gadget id="calculator">180 - 78</gadget>
<output>102</output>

<gadget id="calculator">102 / 2</gadget>
<output>51</output>

<result>51</result>