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You can put this solution on YOUR website!
\n" ); document.write( "A quote from wolframalpha.com:
\n" ); document.write( "There are several definitions of a ray.
\n" ); document.write( "When viewed as a vector, a ray is a vector from a point A to a point B.
\n" ); document.write( "In geometry, a ray is usually taken as a half-infinite line (also known as a half-line) with one of the two points A and B taken to be at infinity.
\n" ); document.write( "Those two definitions will give you different answers to your question.
\n" ); document.write( "(1) With the vector definition above, each ray has two endpoints, so each pair of the 10 points determines two rays -- one in each direction.
\n" ); document.write( "The number of pairs of points is C(10,2)=(10*9)/(2*1)=45
\n" ); document.write( "ANSWER #1: 2*45=90 rays can be drawn using the 10 points.
\n" ); document.write( "(2) With the geometric definition above, each ray has only one endpoint. Since you need a second point to determine the direction of the ray, the 10 points on a line determine 9 rays in each direction.
\n" ); document.write( "ANSWER#2: 2*9=18 rays can be drawn using the 10 points.
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