http://quicklatex.com/cache3/ql_efc8...e92734e_l3.png

need some help getting started. I know how to project, rotate, reflect.

But i´m stuck anyways :)

Thanks!

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- Apr 19th 2011, 05:00 AMmechaniacLinear transformations!
http://quicklatex.com/cache3/ql_efc8...e92734e_l3.png

need some help getting started. I know how to project, rotate, reflect.

But i´m stuck anyways :)

Thanks! - Apr 19th 2011, 05:32 AMFernandoRevilla
Perhaps you meant

**v -> v x u**instead of**u -> v x u**. If so, find first

**v x u = ( v_1 , v_2 , v_3 ) x ( -3 , 2 , 3 ) = ...**

and apply the reflection to**v x u**. - Apr 19th 2011, 08:43 AMmechaniac
oh, its v=(-3,2,3) not u.

- Apr 20th 2011, 06:43 AMmechaniac
Thanks fernando for the help.

So i did it this way:

http://quicklatex.com/cache3/ql_a0ac...19bddb6_l3.png

But its not the correct answer. What did i do wrong? - Apr 20th 2011, 08:19 AMFernandoRevilla
- Apr 20th 2011, 09:07 AMmechaniac
oh i did a misstake with the crossproduct. There is a typo in the T2 matrix to but no worries, got it now! Big thanks :)

- Apr 20th 2011, 03:33 PMHallsofIvy
The simplest way to find a matrix representation of a linear transformation is to look at what the transformation does to the basis vectors. For example, to map <1, 0, 0> onto <1, 0, 0> X <-3, 2, 3> means to map <1, 0, 0> onto <0, -3, -3>. To map <0, 1, 0> onto <0, 1, 0> X <-3, 2, 3> means to map <0, 1, 0> onto <3, 0, 3>. To map <0, 0, 1> onto <0, 0, 1> X <-3, 2, 3> means to map <0, 0, 1> onto <-2, -3, 0>. The matrix giving that is

[ 0 3 -2]

[ -3 0 -3]

[ -3 3 0]

the matrix having those results as columns. To see that, mutiply that matrix by <1, 0, 0>, <0, 1, 0>, and <0, 0, 1> succesivly.

Reflection in x= z maps <1,0, 0> into <0, 0, 1> and <0, 0, 1> into <1, 0, 0>. Since <0, 1, 0> is in that plane, it is mapped into itself.

The matrix giving that transformation is

[ 0 0 1]

[0 1 0]

[1 0 0]

To find the matrix representing both of those transformations, multiply them (in the proper order, of course).