There is at most 1 intersection point when two straight lines intersect, at most 3 intersection points when three straight lines intersect, and at most 6 intersection points when four straight lines intersect. Like this, if ten straight lines intersect, what is the maximum number of intersection points
两条直线相交最多有1个交点，三条直线相交最多有3个交点，四条直线相交最多有6个交点，像这样，十条直线相交，最多交点的个数是多少个
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 10 * 9</gadget>
<output>45</output>

<result>45</result>