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# help me? ocr mei a level vectors

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1. http://www.mei.org.uk/files/papers/2011_June_c4.pdf

im usually okay at vectors but i dont understand 7ii

i get you have to find the angle between the normal vector but it then says horizontal plane, why is this 0 0 1

2. You have to take the normal vector of both and find the angle between them. (0,0,1) is the normal vector of the horizontal plane (z=0)
3. (Original post by ak111)
You have to take the normal vector of both and find the angle between them. (0,0,1) is the normal vector of the horizontal plane (z=0)
where does the 0 0 1 come from though i dont really get it
4. (Original post by liverpool2044)
where does the 0 0 1 come from though i dont really get it
The ground level is represented here as the plane 0x+0y+z=0 (same as z=0). To find the normal vector you always take the coefficients of the x,y and z. The coefficient of x is 0, y is 0 and z is 1 so we get the normal vector to this horizontal plane as (0,0,1)
5. (Original post by ak111)
The ground level is represented here as the plane 0x+0y+z=0 (same as z=0). To find the normal vector you always take the coefficients of the x,y and z. The coefficient of x is 0, y is 0 and z is 1 so we get the normal vector to this horizontal plane as (0,0,1)
why is z the horizontal plane wouldnt that be x?
6. (Original post by liverpool2044)
why is z the horizontal plane wouldnt that be x?
It lies on the x axis but that doesn't make x the horizontal plane. If you think about all the points on the plane, x and y are always changing as you move around the plane but z is always 0 at all points on that plane so the plane has to be z=0.
7. (Original post by ak111)
It lies on the x axis but that doesn't make x the horizontal plane. If you think about all the points on the plane, x and y are always changing as you move around the plane but z is always 0 at all points on that plane so the plane has to be z=0.
ahh okay sorry im being useless here, how do you actually get 0 0 1 then i know you said coefficients but surely the ground level is just zero for all
8. ...
9. (Original post by liverpool2044)
ahh okay sorry im being useless here, how do you actually get 0 0 1 then i know you said coefficients but surely the ground level is just zero for all
Yes the ground level is 0 for z but the normal vector has to be 0,0,1 as it is normal to the plane
10. (Original post by ak111)
Yes the ground level is 0 for z but the normal vector has to be 0,0,1 as it is normal to the plane
finding angle between normal vector and k - it says you get a mark for that

so its the normal vector with k? k is the coordinate on d so can it be worked out from there

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