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# calculate the distance from a point to a line in R3 watch

1. Calculate the distance from P(1,1,1) and L: (0,-5/3,-8/3) + (lambda)(1,1,3)

Ended up with 1/33 sqrt(29^2 +(-26)^2 +(-1)^2). Have ended up with a very weird number!
2. I think you've made an arithmetic mistake somewhere. Also, if I'm not mistaken, the numbers have been chosen so it comes out reasonably nicely.

I suggest you post your working.
3. Bit too slow:

I suspect a sign error - did the same thing myself first time.

I get , now.
4. (Original post by ghostwalker)
Bit too slow:

I suspect a sign error - did the same thing myself first time.

I get , now.
5. (Original post by Lunu)
Subtracting a negative dot product.

As DFranklin suggested, post your working.
6. (Original post by ghostwalker)
Subtracting a negative dot product.

As DFranklin suggested, post your working.
I hope this attaches
Attached Images

7. (Original post by Lunu)
I hope this attaches
You've taken the dot product of a with p, rather than with b.
8. (Original post by ghostwalker)
You've taken the dot product of a with p, rather than with b.
So which two vectors should I use? Very confused!
9. (Original post by Lunu)
So which two vectors should I use? Very confused!
PX, which is "b" in your working - the vector from the point P to a point on the line - and
"a" in your working - the direction vector for the line.

Edit: You worked out b, but then didn't use it.
10. (Original post by ghostwalker)
PX, which is "b" in your working - the vector from the point P to a point on the line - and
"a" in your working - the direction vector for the line.

Edit: You worked out b, but then didn't use it.
Thank you!

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