bort Posted October 15, 2012 Share Posted October 15, 2012 Hello does anyone know how to find the end point of a line segment if you know the starting X,Y coordinate and the distance along the line? Here is a picture to describe. I know the starting (A) and ending ( points of the overall line segment. Now I want to find the new end point of a "sub" line segment that starts at A and follows the same direction for a specified distance. If you can help I would appreciate it very much. Quote Link to comment Share on other sites More sharing options...
enigma# Posted October 15, 2012 Share Posted October 15, 2012 (edited) Given that you have two coordinates (2,5) and (8,2) we assign the values y2 and y1 to the y values and same for x values. y2 = 2 y1 = 5 x2 = 8 x1 = 2 Apply the slope formula: (y2-y1) / (x2-x1 ) = slope(m) (2 - 5)/(8 - 2) (-3) / (6) -3 over 6, slope of -0.5 ---------------------------------------- Now we want our new coordinates, we know that the x value in the new point is 4 (initial distance is 2 already, so add 2 more) so our new coordiantes are (4,y2) and (2,5) so we substitute these values back in, we know the slope is -0.5 so we setup our formula this way, since we know slope (we can replace our slope variable with -0.5) -0.5 = (y2 - 5) / (4 - 2) simplify -.5 = (y2 - 5) / (2) multiply both sides by two to nullify 2 -1 = (y2 - 5) add five to nullify the (-5) on the right side) -1 + 5 = 4 From this answer, we can verify that the y2 coordinate is 4 to verify the slope and thus verify the coordinate (4 - 5) / (4 - 2) simplify (-1)/(2) = -.5 therefore your coordinate is (4,4) Edited October 15, 2012 by enigma# Quote Link to comment Share on other sites More sharing options...
Nevodka Posted October 15, 2012 Share Posted October 15, 2012 sdfghjkl damnit enigma I was going to answer how to do this too Quote Link to comment Share on other sites More sharing options...
-O-P-rime Posted October 15, 2012 Share Posted October 15, 2012 i think you'll be able to understand this better. Quote Link to comment Share on other sites More sharing options...
(Headband)(EG) Posted October 15, 2012 Share Posted October 15, 2012 i think you'll be able to understand this better. Oh Gawd Quote Link to comment Share on other sites More sharing options...
LazaHorse Posted October 15, 2012 Share Posted October 15, 2012 Wow... I was gonna suggest using the given points to find the angle that the line makes with the X-axis and using that angle and the subsequent value of sine and cosine to find the proper x and y values for a given hypotenuse of 2. ... Basic math is too basic now. DX ffffffffuuuuuuuuuuuu Physics Quote Link to comment Share on other sites More sharing options...
Scott Posted October 15, 2012 Share Posted October 15, 2012 Wow... I was gonna suggest using the given points to find the angle that the line makes with the X-axis and using that angle and the subsequent value of sine and cosine to find the proper x and y values for a given hypotenuse of 2. ... Basic math is too basic now. DX ffffffffuuuuuuuuuuuu Physics O.o lol Quote Link to comment Share on other sites More sharing options...
Slowpoke Posted October 15, 2012 Share Posted October 15, 2012 Too late for inb4 enigma and laz Quote Link to comment Share on other sites More sharing options...
jajolt Posted October 15, 2012 Share Posted October 15, 2012 Given that you have two coordinates (2,5) and (8,2)we assign the values y2 and y1 to the y values and same for x values. y2 = 2 y1 = 5 x2 = 8 x1 = 2 Apply the slope formula: (y2-y1) / (x2-x1 ) = slope(m) (2 - 5)/(8 - 2) (-3) / (6) -3 over 6, slope of -0.5 ---------------------------------------- Now we want our new coordinates, we know that the x value in the new point is 4 (initial distance is 2 already, so add 2 more) so our new coordiantes are (4,y2) and (2,5) so we substitute these values back in, we know the slope is -0.5 so we setup our formula this way, since we know slope (we can replace our slope variable with -0.5) -0.5 = (y2 - 5) / (4 - 2) simplify -.5 = (y2 - 5) / (2) multiply both sides by two to nullify 2 -1 = (y2 - 5) add five to nullify the (-5) on the right side) -1 + 5 = 4 From this answer, we can verify that the y2 coordinate is 4 to verify the slope and thus verify the coordinate (4 - 5) / (4 - 2) simplify (-1)/(2) = -.5 therefore your coordinate is (4,4) Yeah this, I knew that Quote Link to comment Share on other sites More sharing options...
bort Posted October 16, 2012 Author Share Posted October 16, 2012 Thanks but I don't know what all those numbers and symbols and colors mean Quote Link to comment Share on other sites More sharing options...
bort Posted October 16, 2012 Author Share Posted October 16, 2012 OK so, i think i'm on to something... Since I know the two points A and B, I can pretend that AB is the hypotenuse of a big triangle that is 3 units high and 6 units long. I can also get the length of the hypotenuse AB by doing that silly distance formula . THEN, since the distance from point A to the mystery point is known (i said it was 2 in the picture), I can basically scale the big triangle down proportionately. Example: If the big hypotenuse was SqrRt(45) or 6.7082039325, then the little hypotenuse of 2 is 3.35410196625 times smaller. So make the legs of 3 and 6 become 3.35410196625 times smaller as well. Quote Link to comment Share on other sites More sharing options...
bort Posted October 16, 2012 Author Share Posted October 16, 2012 Thanks for the assistance. I needed a long time to figure out what u were saying Quote Link to comment Share on other sites More sharing options...
Mike is Fr3sh Posted October 16, 2012 Share Posted October 16, 2012 I would have suggested to just use a ruler. Quote Link to comment Share on other sites More sharing options...
Silly Posted October 16, 2012 Share Posted October 16, 2012 lol mike ^ and jeeze i dont know half of those numbers & symbols Quote Link to comment Share on other sites More sharing options...
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