In an isosceles triangle, the vertex angle is 72°, find the measure of the base angle.
在一个等腰三角形中，顶角是72°，求底角的度数．
<gadget id="calculator">180 - 72</gadget>
<output>108</output>

<gadget id="calculator">108 / 2</gadget>
<output>54</output>

<result>54</result>