geometry help?

Question

Question: Explain how rescue teams could use two of the postulates to locate a distress signal.

Here are the postulates:
Through any two points, there is exactly one line.
Through any three noncollinear points, there is exactly one plane containing them.
If two points lie in a plane, then the line containing those points lie in the plane.
If two lines intersect, then they intersect in exactly one point.
If two planes intersect, then they intersect in exactly one line.

Question 2:
What is the formula for the maximum number of segments determined by n points.

Please be a little more precise. The formula n(n-3)/2 doesn't work.

Answer 1

Use the 1st and 4th one to trangulate and get location at intersection.

Assuming no three points are collinear, the formula is d = n(n-3)/2 , where d is the number of segments and n is the number of points.