Recent content by morphism

  1. M

    Find e^{B} & e^{C}: Matrix Exponentials Homework

    You should look in a linear book (or online) to see how one typically finds eigenvectors. And while you're at it, look up "diagonalization". The point of diagonalization here is this: if D is diagonal, say with entries d_1, ..., d_n down the diagonal, then e^D will be diagonal entries...
  2. M

    Number Theory- arithmetic functions

    What would g be in this case?
  3. M

    Prove or disprove that there is a rational bijective function f : R to (0; 1)

    Sounds like you've pretty much got it. Care to summarize your argument in one post, so we can make sure there are no gaps?
  4. M

    Where could I know something about the active mathematician of a certain field?

    There's no reason to be ashamed. I only wanted to know what flavor of the subject you enjoy before suggesting people/schools. Perhaps you can read up on the different types of representation theory and then let me know which ones strike your fancy. If you're not sure where to begin, I can make...
  5. M

    Relationship between column space of a matrix and rref of matrix

    Each R will be what you get if you do the row operation to the identity matrix. E.g. if you do the row operation that swaps rows 1 and 3, then R will be the identity matrix with rows 1 and 3 swapped.
  6. M

    Relationship between eigenspace and column space

    What if 0 is an eigenvalue? No. Consider ##\left( \begin{smallmatrix} 1 & 1 \\ 0 & 1 \end{smallmatrix} \right)##. If A^2=-I then det(A^2)=det(-I). Try to see if you can use this to answer your question.
  7. M

    Confusion between orthogonal sum and orthogonal direct sum

    I think what's confusing you is the difference between an "internal direct sum" (in which you write a vector space as a direct sum of subspaces) and an "external direct sum" (in which you take two vector spaces and add them together, without reference to them being contained in a larger vector...
  8. M

    Constructing a Normal Series for G from Given Normal Series for N and G/N

    Typically that's referred to as "equivalence", but anyway, your idea does work, i.e. it will produce an equivalent normal series.
  9. M

    Relationship between column space of a matrix and rref of matrix

    The rref of A is of the form GA for some invertible matrix G, so the solution sets to Ax=b and rref(A)x=b will generally be different. The precise fact to note is: if Ax=b then rref(A)x=(GA)x=G(Ax)=Gb. Note that if b=0 then the previous computation yields rref(A)x=0; and conversely, if...
  10. M

    Prove or disprove that there is a rational bijective function f : R to (0; 1)

    A polynomial of odd degree always has a real root, and the denominator can't have a root if we want the rational function to be defined on all of R.
  11. M

    Proving Constant Function f: X → Y is Continuous

    Contradicts what fact? This is fine, but your write-up is sloppy.
  12. M

    What Does RGV Stand For in Casual Communication?

    Can you express the determinant of AB in terms of those of A and B?
  13. M

    Constructing a Normal Series for G from Given Normal Series for N and G/N

    What does it mean to say that two normal series are isomorphic?
  14. M

    Prove or disprove that there is a rational bijective function f : R to (0; 1)

    A rational function is the ratio of two polynomials. You observed if there's anything "funky" in the denominator, then certainly R won't get mapped to (0,1). Now just think about what "funky" really means.. Remember, the denominator is a polynomial. Edit: Sorry--that's not really helpful...
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