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FP3 June 2013

Hi can someone please explain how to find b for question 8 part c for June 2013?

I have found A easily but don't understand how to get the B value?

https://2d31ca6ec4f6115572728c3a9168ad5dfc897f33.googledrive.com/host/0B1ZiqBksUHNYSjAyWFYyQmU5Tjg/Edexcel-Set-2/Ch.5%20Vectors.pdf

Reply 1

TeeEm

Original post by Teddysmith123

please show some workings and I will check/help

Reply 2

Teddysmith123

Original post by TeeEm

please show some workings and I will check/help

Ok so for A I found N by multiplying the N values together to get A = -2i+5j+13k

So now that I have done this I know that r*(-2i+5j+13k)=B

So how do I get B now from what I have done

Reply 3

TeeEm

Original post by Teddysmith123

Ok so for A I found N by multiplying the N values together to get A = -2i+5j+13k

So now that I have done this I know that r*(-2i+5j+13k)=B

So how do I get B now from what I have done

(r - a) x d = 0
r x d - a x d = 0
r x d = a x d

a = point on line
d = direction vector of line
r = arbitrary point on line

the required answer is in red