There are 10 points on a circle, and every two points can be connected with a line segment, how many line segments can be connected in total.
在一个圆周上共有10个点，每两个点可以连接一条线段，则一共可以连出多少条线段．
<gadget id="calculator">1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9</gadget>
<output>45</output>

<result>45</result>