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M1 doubt

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sweetest angel:
june 2009 Q2 b) (attached)

this is the answer

R = (i - 3j) + (pi + 2pj) = (1 + p)i + (-3 + 2p)j
R is parallel to i ? (-3 + 2p) = 0
? p = 3/2

but i dnt get it. if R is parallel to i then the value of i=0 not j=0 ?

T.Q:

--- Quote from: sweetest angel on December 16, 2009, 05:54:15 am ---june 2009 Q2 b) (attached)

this is the answer

R = (i - 3j) + (pi + 2pj) = (1 + p)i + (-3 + 2p)j
R is parallel to i ? (-3 + 2p) = 0
? p = 3/2

but i dnt get it. if R is parallel to i then the value of i=0 not j=0 ?

--- End quote ---

because i  is a straight horizantal line so it will have a zero j
and because R is parallel to i ,then R will have the value of j equal to zero
thats why they took the j value equal to zero

sweetest angel:
ohhhhh...but we dnt knw if it passes through j or not so maybe it has a j value  ???

eightAs:

--- Quote from: sweetest angel on December 16, 2009, 04:40:13 pm ---ohhhhh...but we dnt knw if it passes through j or not so maybe it has a j value  ???

--- End quote ---
consider the whole set up on the
consider an arbitrary vector and the unit vector
We assume both vectors are parallel.
Lets assume the arbitrary vector is +
Gradient of = Gradient of the other vector

Thus if an arbitrary vector and are parallel, the co-effecient of j for the arbitrary vector has to equal 0.

Ghost Of Highbury:

--- Quote from: sweetest angel on December 16, 2009, 04:40:13 pm ---ohhhhh...but we dnt knw if it passes through j or not so maybe it has a j value  ???

--- End quote ---

a vector (2D) has two components; i and j which define its direction.
It cannot "PASS" through j. its a component. It can pass through a point.

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