# I forgot what the formula for this is.

If I give you a function f(x) (cartesian) and I ask you to rotate it about the x axis (counterclockwise) by an angle phi, what is the new function formula?

I remember I did this with matrices, but I can't remember the one for functions. For convenience, let angle phi be 0, pi/2, 3pi/2, and 2pi.

I am guessing 0 would remain the same. I just don't know how to use matrices on functions.

Does anyone understand my question?

## Answers and Replies

There's obviously $SO(n)$ but that's matrices.

Doesn't Euler's formula do that same thing?

$e^{i\theta} = cos\theta + isin\theta$

EDIT: Euler's formula is only for complex numbers.

Yes, but for functions. Is there no equivalence? I kinda had something like this for conics

There's obviously $SO(n)$ but that's matrices.

Doesn't Euler's formula do that same thing?

$e^{i\theta} = cos\theta + isin\theta$

EDIT: Euler's formula is only for complex numbers.

No real numbers please

Hhhmmm...if you have a set of points, I can see being rotated with a transformation matrix...but a function? If you have a function f(x) and you "rotate" it 90 degrees...chances are it will stop being a function!...at least, in the sense of the new fnew(x) = trans(forig(x))

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