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[CIE] All Pure Mathematics (P1, P2 and P3) doubts here !

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astarmathsandphysics:
Tabke abc as  (-1, 2, 5) - (2, -2, 11)=(-1-2,2--2,,5-1)=(-3,4,4)
a=-3
b=4
c=4

Alpha:

--- Quote from: Deadly_king on October 16, 2011, 06:50:42 am ---I don't think I'll be of much help since I've forgotten most of my Maths by now :-\

Anyway I'll try as much as I remember though am not so sure.....

To find the angle between a line and a plane we first have to find the angle between the normal of the plane and the direction vector of the line.

We need to find the direction vector of the normal of the plane by using OA and OB -----> OB - OA

Then you use the formula to find angle ;)

--- End quote ---

Normal and direction vectors, sin formula, yes, I did.:)

But in the ER, OA is multiplied by OB. Gives you the answer, but I don't understand why. :-\

No worries. Thank you though. :)



--- Quote from: astarmathsandphysics on October 16, 2011, 10:35:37 am ---Tabke abc as  (-1, 2, 5) - (2, -2, 11)=(-1-2,2--2,,5-1)=(-3,4,4)
a=-3
b=4
c=4

--- End quote ---

(-1-2,2--2,,5-11)
c= -6. ;)

I get what you mean. I did that too.

http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9709%20-%20Mathematics/9709_s11_er.pdf

The examiners' report, on pg 22. It says by multiplying OA and OB. This is what I don't get. :-\
Even YA's best contributors do not. :(

Appreciate your help. Thank you Sir.  :)

astarmathsandphysics:
Do thety mean the cross product?

Alpha:

--- Quote from: astarmathsandphysics on October 16, 2011, 09:34:08 pm ---Do thety mean the cross product?

--- End quote ---

No, scalar product is the dot product. They use |OA|.|OB| cos Angle= OA.OB

I checked this method. It does give you the answer. But I still don't find any logic. :-\

astarmathsandphysics:
I recognize this question from a p4 paper I did today. Attached.

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