# the point of intersect two lines

Discussion in 'Math' started by aven, Feb 3, 2010.

1. ### aven Thread Starter New Member

Feb 3, 2010
2
0
Hello all
I'm new here and my english is also not very good, but I hope I can articulate my question anyway.

pls, how i drived the an equation for evaluating if any two straight lines are intersecting or no.

2. ### KL7AJ AAC Fanatic!

Nov 4, 2008
2,182
415

No problem. Your English is probably much better than my whatever-it-is-you-speak.

This can be done with simultaneous equations. Write the equation for each line in the form y=mx + b

Calculate the slope m for each line.

If m is the same, the lines are parallel. If m is different, they intersect somewhere. Simple as that!

eric

3. ### Papabravo Expert

Feb 24, 2006
11,946
2,560
Packages like Matlab or Scilab can solve those simultaneous equations for the intersection point if the slopes are different. This is another way of saying that the coefficient matrix has a non-zero determinant.

4. ### ELECTRONERD AAC Fanatic!

May 26, 2009
1,146
16
I might add that if you want to find two perpindicular lines you can still use the y = mx + b formula. However, perpindicular lines will be the negative square root of your other equation.

Austin

5. ### studiot AAC Fanatic!

Nov 9, 2007
5,003
521
Lines which do not intersect are either parallel or skew.

Eric's answer is for lines drawn on graph paper - Lines in 2 dimensions. There are no skew lines in 2D. All pairs of non intersecting lines are pairs of parallel lines.

In 3D lines which do not intersect and are not parallel are called skew lines.
The simplest way to find out if two lines in 3 D do not intersect is to calculate the distance between them. If this = 0 they intersect, if it is +ve and nonzero they do not.