The diameter of a semicircle is 8 cm, find the area of the isosceles triangle in the semicircle.
一个半圆的直径是8cm，求半圆中等腰三角形的面积．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>