Comments

1. Hi, Lara, I think I can help with this one. (I'm assuming you're talking about a line segment here.)
   

   If you check out the Cramlet on Midpoint of a Line Segment, you'll see that given two endpoints at (x1, y1) and (x2, y2) the coordinates for the midpoint (x,y) are defined as (x1+x2)/2, (y1+y2)/2. We can use this formula to work backwards to find the other end point (x2, y2) of your line segment.

   First, we'll use the 'x' part of the formula to solve for x2:

   • (x1+x2)/2 = x
     

   Multiply both sides by 2 to get:

   • x1+x2 = 2x
     

   Now subtract x1 from both sides to solve for x2:

   • x2 = 2x - x1

   If you repeat the same steps for the 'y' part of the coordinate you'll get a similar result:

   • y2 = 2y - y1 

   Just plug the values for your end point (x1,y1) and your mid point (x,y) and you'll get the coordinates for your other end point.

   (Just to be sure, you can plug your two end points into the Midpoint of a Line Segment Cramlet to doublecheck your answer.)

   I hope that helped. 

   Rudy on Friday, 19 September 2008, 08:02 CDT # |