An arch bridge, viewed from the side in a semicircle. The radius of this semicircle is 15m, what is the length of the semicircular arch of the bridge?
一座拱桥，从侧面看呈半圆形．这个半圆的半径是15m，这座桥的半圆形拱长是多少？
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 15 * 1</gadget>
<output>47.1</output>

<result>47.1</result>