In a right triangle, the degree ratio of the right angle to one of the acute angles is 9:4, what is the degree of the other acute angle.
在直角三角形中，直角和其中一个锐角的度数比是9：4，另一个锐角是多少度．
<gadget id="calculator">90 / 9</gadget>
<output>10</output>

<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">90 - 40</gadget>
<output>50</output>

<result>50</result>