The sum of the apex and base angles of an isosceles triangle is 135 degrees. What is the sum of the interior angles of the apex of this triangle?
一个等腰三角形的顶角和一个底角和是135度，这个三角形的顶角度数是内角和的多少
<gadget id="calculator">180 - 135</gadget>
<output>45</output>

<gadget id="calculator">135 - 45</gadget>
<output>90</output>

<gadget id="calculator">90 / 180</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>