The ratio of one base angle to one apex angle of an isosceles triangle is 4:1. What is the base angle of this triangle.
等腰三角形一个底角和一个顶角度数的比是4：1．这个三角形的底角是多少度．
<gadget id="calculator">4 + 4 + 1</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">180 * (4/9)</gadget>
<output>80</output>

<result>80</result>