# Thread: Can someone help with rotations and matrices?

1. ## Can someone help with rotations and matrices?

Lecturer and workbook is all over the place and legitimately no concrete examples whatsoever, its approaching exam time so im trying to actually start revision in depth but workbook is full of incoherent shit holy crap. I swear im not retarded lol, there was a subject feedback thing and massive majority of students said the subject is totally incoherent and never finishes explaining anything and lecturer is a rambling ghoul.

can someone direct me how to do these pls? am looost

https://imgur.com/a/NBAJU

2. ## Re: Can someone help with rotations and matrices?

Originally Posted by hayabusaboston
Lecturer and workbook is all over the place and legitimately no concrete examples whatsoever, its approaching exam time so im trying to actually start revision in depth but workbook is full of incoherent shit holy crap. I swear im not retarded lol, there was a subject feedback thing and massive majority of students said the subject is totally incoherent and never finishes explaining anything and lecturer is a rambling ghoul.

can someone direct me how to do these pls? am looost

https://imgur.com/a/NBAJU

I got 1 and 2 a,b but not c, 3,4 plsss general directions appreciated <3

3. ## Re: Can someone help with rotations and matrices?

Originally Posted by hayabusaboston
I got 1 and 2 a,b but not c, 3,4 plsss general directions appreciated <3
Well for 2(c) for example, you should be able to show it's not linear by giving a specific example (it's basically not linear because the "length" function is not linear).

And for 4, make sure to be familiar with the definitions of injective, surjective, and invertible (and it'll help to know about properties of these for linear maps based on the dimensions of the domain and codomain).

4. ## Re: Can someone help with rotations and matrices?

for 3 a)

is D matrix

(0,1,0,0...)/(0,0,2,0...)/(0,0,0,3...)?

and M

(1,0,0,0...)/(0,0,0,0...)/(0,1,0,0...)

What is DoM btw?

5. ## Re: Can someone help with rotations and matrices?

Originally Posted by hayabusaboston
What is DoM btw?
$\noindent It's just a notation for function composition. The notation D\circ M refers to the composition of D and M. In general, f\circ g basically means the function whose values are f(g(x)) (assuming appropriate domains/codomains). You can find out more and see examples on the Wikipedia page:$

https://en.wikipedia.org/wiki/Functi...ition#Examples .

6. ## Re: Can someone help with rotations and matrices?

Preez direct some1?

7. ## Re: Can someone help with rotations and matrices?

WEll I googled and got them all eventually after reading the theory. Lol.

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