If the apex angle of an isosceles triangle is 78°, what is the base angle?
一个等腰三角形的顶角是78°，它的一个底角是多少．
<gadget id="calculator">180 - 78</gadget>
<output>102</output>

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

<result>51</result>