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# P6 - Matices Revision (P6) watch

1. Hi,

Im struggling with the Matrices part of P6 I know how to times add subtract etc them but im stuggling with transformations, determinants of 3 x 3 matrices and inverses of matrices, if any revision websites or notes or points in the right direction would help me out SO MUCH.

Many Thanks

Streety
2. (Original post by streetyfatb)
Hi,

Im struggling with the Matrices part of P6 I know how to times add subtract etc them but im stuggling with transformations, determinants of 3 x 3 matrices and inverses of matrices, if any revision websites or notes or points in the right direction would help me out SO MUCH.

Many Thanks

Streety
Is this edexcel? The edexcel matrix stuff is straightforward manipulation techiniques that simply need to be learned. Do you have a textbook for your syllabus?
3. (Original post by streetyfatb)
Hi,

Im struggling with the Matrices part of P6 I know how to times add subtract etc them but im stuggling with transformations,
a few bits,
1.they give you the general transformations for reflections and rotations in the formula book
2. if the determinent is negative it is a reflection
3. determinent gives you the area scale factor

determinants of 3 x 3 matrices
are you ok doing the vector product with vectors? its exactly the same thing but with a 3x3 grid of all numbers and not an i,j,k on the top

and inverses of matrices,
2x2 - swap leading diagonal values and make other 2 negative (from what they were) then divide whole by determinent of original matrix

3x3 - label columns a,b, and c, do cross product on pairs, then put these into the rows of your new matrix in this order:
bxc
cxa
axb
then divide by determinent of original matrix

Lucy x
4. Hi thanks for that, the exam board is OCR and the exam is tomorrow, im taking P6, P3 and D1, im just dreading the matrice questions.
5. (Original post by streetyfatb)
Hi thanks for that, the exam board is OCR and the exam is tomorrow, im taking P6, P3 and D1, im just dreading the matrice questions.
Ahh, i see. From the little I know some of the OCR material is more complex than the edexcel so you probably do things I don't even know about...
From the post by Ventricles I see you have a different method for finding the inverse of a matrix to that given in the P6 heinemann book. It seems much faster but i'll probably play safe and stick with my current method for my exam.
6. (Original post by Gaz031)
Ahh, i see. From the little I know some of the OCR material is more complex than the edexcel so you probably do things I don't even know about...
From the post by Ventricles I see you have a different method for finding the inverse of a matrix to that given in the P6 heinemann book. It seems much faster but i'll probably play safe and stick with my current method for my exam.
We were actually taught a different method- where you put the identity next to the matrix and then turn the matrix into the identity using row additions etc. but we got upset and found the other method (Ventricles') which seems like quite a bit of working but works every time x
7. (Original post by Ventricles)
a few bits,
1.they give you the general transformations for reflections and rotations in the formula book
2. if the determinent is negative it is a reflection
3. determinent gives you the area scale factor

Lucy x
they give us the general thingys!! grrrrrrrrr y did no one tell me
8. (Original post by undercover-ange)
We were actually taught a different method- where you put the identity next to the matrix and then turn the matrix into the identity using row additions etc. but we got upset and found the other method (Ventricles') which seems like quite a bit of working but works every time x

Hmmmm; for a 2x2 obviously theres the standard method:

A-1 = .

For 3x3 or bigger I have to admit to using Elementary Row/Column Operations on an augmented matrix:

A | In ===> In | A-1

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