• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Vector discussion...

Messages
2,703
Reaction score
3,939
Points
273
can any one tell me te formulae to find the distance etween two planes in vectors????
 
Messages
1,394
Reaction score
1,377
Points
173
upload_2014-5-15_13-56-26.png

I got lamda=3 but not lamda=1 :/

also in the first isnt it enough to show that the scalar product of DV of l and normal of m equals 0??
what have they written here in the marking scheme...


upload_2014-5-15_13-58-51.png
 
Messages
4,493
Reaction score
15,418
Points
523
found it!
done by sumone else
We have to find the point p where the perpendicular distance to the two planes is same.


first we will for an equation the way the paper gave.
therefore
for plane m
|x+2y-2z-1|/sqrt((1^2) + (2^2) + (-2^2) = |x+2y-2z-1|/3 [P.S, sqrt is square root]
for plane n
|2x-2y+z-7|/sqrt((2^2)+(-2^2)+(1^2) = |2x-2y+z-7|/3


since you are finding a point where both distance is same , therefore.
|x+2y-2z-1|/3 = |2x-2y+z-7|/3 (3 can be cancelled both sides)
=
|x+2y-2z-1| = |2x-2y+z-7|

now we will sub the line values in the equation.
the x component (1+2t) [P.S, t is lamda ]
the y comp. (1+t)
the z comp. (-1+2t)

therefore.
| (1+2t) +2 ( 1+t) -2(-1+2t) -1 | = |2(1+2t) - 2(1+t) + (-1+2t) - 7 |
simplifying it you get
|4| = |-8+4t|
now to solve modulus, we do squaring method
16 = 64-64t+16t^2
simplify
2 = 8 - 8t +2t^2
2t^2 - 8t + 6 = 0
solve it and get
t = 3 or t= 1
when t=3 the position of point is [P.S, u do this by sub t value in line equation)
(7, 4, 5) => OA
when t = 1 the position of point is
(3, 2, 1) => OB

BA (or AB, same thing) = OA - OB
= (4 , 2, 4)

now find the mod
sqrt(4^2 + 2^2 + 4^2)
= 6
 
Messages
1,394
Reaction score
1,377
Points
173
oohh okaa
found it!
done by sumone else
We have to find the point p where the perpendicular distance to the two planes is same.


first we will for an equation the way the paper gave.
therefore
for plane m
|x+2y-2z-1|/sqrt((1^2) + (2^2) + (-2^2) = |x+2y-2z-1|/3 [P.S, sqrt is square root]
for plane n
|2x-2y+z-7|/sqrt((2^2)+(-2^2)+(1^2) = |2x-2y+z-7|/3


since you are finding a point where both distance is same , therefore.
|x+2y-2z-1|/3 = |2x-2y+z-7|/3 (3 can be cancelled both sides)
=
|x+2y-2z-1| = |2x-2y+z-7|

now we will sub the line values in the equation.
the x component (1+2t) [P.S, t is lamda ]
the y comp. (1+t)
the z comp. (-1+2t)

therefore.
| (1+2t) +2 ( 1+t) -2(-1+2t) -1 | = |2(1+2t) - 2(1+t) + (-1+2t) - 7 |
simplifying it you get
|4| = |-8+4t|
now to solve modulus, we do squaring method
16 = 64-64t+16t^2
simplify
2 = 8 - 8t +2t^2
2t^2 - 8t + 6 = 0
solve it and get
t = 3 or t= 1
when t=3 the position of point is [P.S, u do this by sub t value in line equation)
(7, 4, 5) => OA
when t = 1 the position of point is
(3, 2, 1) => OB

BA (or AB, same thing) = OA - OB
= (4 , 2, 4)

now find the mod
sqrt(4^2 + 2^2 + 4^2)
= 6
yy.. i was ignoring the modulus and simply solving it..
thankss a lott man!!
sooo many prayers for!! :')
 
Messages
2,703
Reaction score
3,939
Points
273
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_qp_31.pdf

Q8

I found the general point 'N' for PN
PN is the perpendicular line from P to l

I dont know wat i'm doing wrong after that... i have taken the scalar product as zero

[(2+2n)i + (n-1)j + (3n-15)k] * (2i+j+3k) = 0

but my value for n is not coming out to be n=3
it is n = -48/14 :sick:
if you dont stop posting question after question your gona scare me to the moon -_-
 
Messages
191
Reaction score
175
Points
53

Attachments

  • pg1.jpeg
    pg1.jpeg
    189.3 KB · Views: 10
  • pg2.jpeg
    pg2.jpeg
    174 KB · Views: 10
  • pg3.jpeg
    pg3.jpeg
    129.8 KB · Views: 5
Top