# Calculate perpendicular vector

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I'm having a little difficulty with some matrix maths. I have 3 points P0, P1 and P2 [as in the attached drawing] and I need to find the point on the line between p0 and p1, such that the line from it to P2 is perpendicular to it.

The way I tried is to first find the angle between P0-->P1 and P0-->P2 [acos of the dot product], then from there find the lengths a, o and a using trig, from there it's simple to find the correct position but somewhere or other I'm going wrong.

I'll persevere but I wondered if there is some standard function to find that position, I imagine it must be a common thing to want to do...

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I figured it out, I had a plus instead of a minus...

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Hey is it possible for you to attach your hip file for me too see how you did it?

Thank you.

Regards

Varisht

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Posted (edited)

I don't have that particular file to hand any more but I made you a file to demonstrate an easier method.

If you take the dot product of the normalized vector P0->P1 in the drawing above, and the UNnormalized vector P0->P2 that will give you the magnitude of the vector in the (normalized) direction P0->P1 that the perpendicular projection point is. That's probably a bit garbled but if you look at the file I hope it will make sense...

Edited by j00ey

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