RE: Beginner Question
- To: mathgroup at smc.vnet.net
- Subject: [mg66588] RE: [mg66561] Beginner Question
- From: spiraltooth <spiraltooth at optonline.net>
- Date: Sun, 21 May 2006 00:29:33 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
xA=x(A)
xB=x(B)
xC=x(c)
yA=y(A)
yB=y(B)
yC=y(C)
m=(yA-yB)/(xA-xB)
b=yA-(m*xA)
If[xC-((yC-b)/m)<0,Left,Right]
For example if point A is {1,2} and point B is {2,3} and point C is {3,4}:
xA = 1
xB = 2
xC = 3
yA = 2
yB = 3
yC = 4
m = (yA - yB)/(xA - xB)
b = yA - (m*xA)
If[xC - ((yC - b)/m) < 0, Left, Right]
Out[1]=
1
Out[2]=
2
Out[3]=
3
Out[4]=
2
Out[5]=
3
Out[6]=
4
Out[7]=
1
Out[8]=
1
Out[9]=
Right
Best regards,
Alan
-----Original Message-----
From: akil [mailto:akil39 at gmail.com]
To: mathgroup at smc.vnet.net
Subject: [mg66588] [mg66561] Beginner Question
Hi,
Suppose I have three 2D points A, B, C.
And two points, namely A and B form a line.
How can I determine in mathematica on which side, (so which half-plane
formed by) of the line, point C is.
So when I input three points I want to know if the third point is on the
left or right side of the half plane formed by the line (ray) A,B.
Appreciate any help.