Given that the apex angle of an equilateral triangle is 72°, what is its base angle?
已知一个等要三角形的顶角是72°，那么它的底角是多少°．
<gadget id="calculator">180 - 72</gadget>
<output>108</output>

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

<result>54</result>