Need math (Trig?) help

I'm mathematically challenged! Need some help on how to calculate a vector that's a given distance between two known vectors.

example:
vector vMyPos = llGetPos();
vector vYourpos = <some vector way over there...>

What I need is a formula to find a position in between the 2 known vectors, at a given distance. If you are 50m from me, I want to find the pos that's 13m from my pos, on a direct line to your position.

--Bos

I found this in another thread, you might find it helpful:

// By Chris Omega
vector setVectorDistance(vector destination, float distance) {
    if (llVecDist(llGetPos(), destination) < distance) {
        return destination;
    } else {
        // Argh, we actually have to do math.
        vector offset = destination - llGetPos();
        return llVecNorm(offset) * distance + llGetPos();
    }
}

Here's something that might help for your problem specificly:

vector shortenVector(vector startPoint, vector endPoint, float distance) {
    vector offset = endPoint - startPoint;
    return llVecNorm(offset) * distance + startPoint
}

You don't need trig for that.

There's a quick way to do it - using something similar to how you take an average.

So if you do:
(you + me)/2 you get the point halfway between us (the average).

If you want something x metres away from me, in the direction of you, where d is llVecDist(you, me), it is:

(x/d)*me + (1-(x/d))*you

If you stick in x = d/2 (that is you want the midpoint between us) then you'll see that it comes out to be just the average.

just use vector norm.

me + (llVecNorm(you - me) * desired_distance)

Thanks guys
Will give those samples a run. I really should have paid attention in school... alas, the beach was too close by.

--Bos