Lines

[SteveD73]

Hello

Can anyone answer the following question:

I have 2 lines with the following coords

line 1 (x1, y1) - (x2, y2)
line 2 (x1, y1) - (x3, y3)

How can I calculate the angle between them?

Thanks

 

[tchouch]

For two Vectors v1(x1, y1, z1) and v2(x2, y2, z2):

cos(v1, v2) = (x1*x2 + y1*y2 + z1*z2)/(sqrt(x1*x1 + y1*y1 + z1*z1) *sqrt(x2*x2 + y2*y2 + z2*z2));

 

[SteveD73]

I've tried the above formulae with no success. If the coords of the lines are

(0, 0) - (10, -10)
(0, 0) - (10, 10)

The angle should be 45. However, the first part of equation (x1*x2 + y1*y2 + z1*z2) results in 0.

0/x = 0

Any sugestions on where im going wrong?

Thanks

 

[Cagliostro]

as I see, there is 90 degrees, not 45. 45 are relative to OX or to OY, but not between themselves. Ion Filipski

filipski@excite.com